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LYLEM. THORPE
STATE OF ILLINOIS
DEPARTMENT OF REGISTRATION AND EDUCATION
DIVISION OF THE
NATURAL HISTORY SURVEY
STEPHEN A. FORBES. Chief
Vol. XIII.
BULLETIN
Article XV.
The Small Bottom and Shore Fauna of the
Middle and Lower Illinois River and
its Connecting Lakes, ChiUicothe to
Grafton: its Valuation; its Sources
of Food Supply; and its Relation
to the Fishery
BY
ROBERT E. RICHARDSON
GOVEKNiVltNT
RECEIN1
APR 2 6
UMIVERS1TY l|
UHjV£F31TY OF CX
PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS
V
URBANA, ILLINOIS
June, 1921
983
BRARY
NNECTiCUT
CONTENTS
PAGE
Introduction 363
General summary 366
Hydrography and bottom fauna, Illinois River, Chillicothe to Grafton,
July— October, 1915 376
(a) Chillicothe to foot of Peoria Lake (18.5 miles) 376
(b) Foot of Peoria Lake to Pekin (9 miles) 386
(c) Pekin to Copperas Creek dam (16.2 miles) 388
(d) Copperas Creek dam to Havana (16.8 miles) 392
(e) Havana to Lagrange dam (42.5 miles) 398
(/) Lagrange dam to Grafton (77.5 miles) 404
(g) General summary, Illinois River bottom fauna, July — October,
1915 409
The bottom fauna of the lakes and ponds of the Illinois River bottom-
lands between Copperas Creek dam and Lagrange, July — October,
1914—1915 418
The weed fauna of the 1 — 4 foot zone of the Illinois valley lakes, and the
combined bottom- and weed-fauna average, August — October, 1914 431
The bottom and weed1 fauna of the littoral zone of the deep glacial lakes
of northeastern Illinois, August — October, 1916 433
Comparison with outside bottom- and weed-fauna valuations -435
The food of certain small bottom-invertebrates in the river channel
at Havana and the general composition of the detritus 439
The nitrogen, organic carbon, and other oxidizable matter in the bottom
muds of the river and lakes below Chillicothe, 1913 — 1914 444
The plankton and other limnetic oxidizable matters carried by the Illi-
nois River channel at Chillicothe and Havana, 1909 — 1914 448
General comparison of the Illinois River and the connecting lakes in the
food resources of a fishery and in fish output 462
The reproductive rate of the bottom animals 472
Changes in the quantity of the bottom-fauna stocks between 1913 and 1915 474
Detailed valuation tables:
I. Bottom Fauna, Illinois River, 1915 477
II. Bottom fauna of the lakes of the Illinois valley, Copperas Creek
dam to LaGrange, 1914 — 1915 494
III. Weed fauna, 1- to 4-foot zone, lakes and backwaters in vicinity
of Havana, 1914 512
IV. Bottom and weed fauna, littoral zone of glacial lakes of north-
eastern Illinois, 1916 515
Bibliography 522
Profile of Illinois River, Chillicothe to Lagrange dam.
Maps of Illinois River and bottom-land lakes, Chillicothe to Grafton.
Article XV. — The Small Bottom and Shore Fauna of the Middle
and Lower Illinois River and its Connecting Lakes, Chillicothe to Graf-
ton: its Valuation; its Sources of Food Supply; and its Relation to the
Fishery. By Robert E. Richardson.
Introduction
The present paper, so far as it relates particularly to the valuation of
the bottom and shore animals, brings together the results of three sum-
mer-autumn seasons of dredging operations in the Illinois River and its
connecting backwaters, July, 1913, to October, 1915. The work in the
river proper and in the wide expansion of its waters known as Peoria
Lake included forty cross-sections, at intervals ranging from one to about
eleven miles, covering the lower one hundred and eighty miles of the
river, or about 80 per cent, of the total distance- between the mouth and
the head of navigation at La Salle ; and embraced a total of three hundred
and eighty-seven dredge and dipper collections. The dredging opera-
tions in the more inclosed bottom-land lakes were mainly confined to
those in the middle Illinois valley district of about fifty-nine miles river
length between the Copperas Creek and Lagrange dams, in the lakes and
other backwaters of which region three hundred and eighty-five dredge
and dipper hauls were taken during the three working seasons.
In addition to the collections of the bottom animals for the valua-
tion studies, sieved samples of the mud deposits on the floor of both the
river and the lakes were taken in 1913 and 1914 and analyzed for such
indications as they might contain of reasons for differences in productiv-
ity of different bottom areas. Between M.arch, 1914, and February, 1915,
also, standard sanitary chemical analyses of water samples from a lim-
ited number of stations in the upper, middle, and lower river were car-
ried on continuously at weekly intervals with a view particularly to
obtaining data on the nitrogen load of the waters and on the rate of
progress of its nitrification. Such comparisons as are undertaken Avith
plankton production are with reference mainly to data collected in 1909
and 1910, the most recent seasons devoted at all extensively to plankton
operations in the region of the river covered by" the present paper. Some
principal conclusions from the plankton work of these two years in the
river and lakes at Havana, as also from the sanitary chemical analyses of
1914-1915, have already been reported upon in papers by Prof. Forbes and
the present writer (Forbes and Richardson, 1913; 1919).
Apparatus. — The collection of the bottom fauna was begun in the
summer of 1913 with our ordinary iron dredges (modified "Blake" or
364
"Naturalist's" type (see pages 367, 368), supplemented in some situa-
tions where there was unusually soft mud and where the heavier framed
iron dredges were inclined to sink too deeply and fill too quickly, with a
lighter framed dredge following closely a recent design by Ekman which
was intended for quite a different purpose. (See Fig. 3 and 4.)
Although there was no expectation early in the work of making
more than a very rough quantitative application of the biological data
obtained, all the dredge hauls were, from the first, of a previously de-
termined and recorded length. The introduction into use in the summer
of 1914, for work in water under eighteen feet in depth, of the "mud-
dipper" (see Fig. 5), an instrument bearing some resemblance to
the Walker dipper-dredge as used by Baker (1916, 1918), and the adop-
tion of finer meshed inner bags for it and the dredges, was the means of
what appeared to be rather more accurate work that year than in the
first season, while at the same time its use in parallel test hauls of differ-
ent lengths alongside the iron dredges suggested that averaged results
from measured drags, under certain limits of length, with either, had a
greater quantitative value than we had at first believed. It was found,
in brief, that with a 22" X 6" front iron dredge we took on the average
as many bottom animals by hauling five feet as by hauling ten, and with
a 6-inch mud-dipper as many in two feet as in four, but that
in hauls under two or five feet, in either case, we got less. As the aver-
age 5-foot haul with the dredge was in the neighborhood of ten times the
2-foot drag of the dipper, and the 2-foot dipper haul about five times a
quick deep dip of the mud-dipper to a depth of about three inches (ap-
proximate area covered, 25 square inches), it was an easy step to the con-
clusion that on a rough average, if a few apparently aberrant cases be
excluded, the most of the 5- to 10-foot dredge hauls might be safely
taken to represent an effective drag of about one square yard, and the
2- to 4-foot hauls of the dipper an effective drag of about 0.1 square
yard (125 to 130 square inches). Still more recent parallel tests of the
dipper alongside a new Petersen self-closing bottom sampler have not
served materially to change these conclusions.
The method used for collecting the small weed animals in the zones
of densest vegetation (usually in water under four feet deep) was in-
complete, taking in only the small fauna within the 0 to 9-inch depth line.
A large bucket of known depth and diameter was lowered about the tops
of the plants, the stems were cut off underneath, and then the bucket
was brought into an upright position quickly ; after which the weed-tops
were shaken out in the water saved, and that was finally passed through
a 120-mesh sieve. Pulling up the weeds entire in- water over two and a
half feet deep had shown that the attached weed animals, whether snails,
insect larvae, or Crustacea, were, in bulk at least, decidedly most abun-
dant nearer the top. And the adoption of the method also followed, by
necessity, some unsatisfactory experience in the use of a small 3-legged
caisson and pump — which involved the handling of vastly more material
365
than was practicable, with also an annoying tendency to in-leakage of
outside water at the bottom.
Valuation. — The determination to undertake a valuation of the bot-
tom invertebrate populations that come within the feeding horizon of our
ordinary bottom-feeding fishes in terms of pounds per acre was made
some time after the conclusion of our field work in 1915, and has been
carried out on a basis of estimated average-sized specimens of the va-
rious species as they ran in a relatively small number of typical midsum-
mer collections weighed after more than a year's preservation in alcohol
and formalin. An average correction of 25 per cent, for loss in weight
in alcohol (on a base of body weight only for Mollusca, and on a base
of gross weight for other groups) has been made, after a limited number
of experimental weights, in the preserved and the fresh state, of a few
snails and insect larvae. The final valuation figures, so far as they in-
clude insects, their larvae or other immature forms, worms, or Crustacea,
represent gross rough weights, but in the case of the Mollusca (Gastrop-
oda, Sphaeriidae, or young Unionidae) represent the body weight only,
after deduction of shell weights at rates determined separately for each
species by actual weighing. Sponges, Bryozoa, and other smaller in-
crusting invertebrates are not included in the valuation figures ; as are not
also crayfish or pearl-button mussels, except the young.
Acknowledgments. — For many of the hydrographical and physical
data we are indebted to the U. S. Army Engineers' survey of 1902 — 1905
(House Document 263, 59th Congress, 1st session, and accompanying
charts) ; as well as to Alvord and Burdick's recent excellent report
(1915) on the Illinois River and its bottom-lands; and, in a lesser de-
gree, to the Report of the Legislative Committee on submerged and shore-
lands (1911). Thanks are also due Dr. Edward Bartow, Chief of the
State Water Survey, for his interested cooperation in obtaining the san-
itary chemical analyses of river waters in 1914 ; and to Prof. S. W. Parr
for supervising the analysis of the bottom mud samples taken that year
and the year preceding. To Mr. Charles A. Hart is owing a special debt
for his assistance in the determination of much of the more unfamiliar
biological material of the earlier collections, taken in the preliminary
field work of July-September, 1913. Mr. F. C. Baker has contributed
both facts and opinions that have made possible rough valuations, for
comparison with our own, of the littoral bottom fauna areas of the lower
south bay of Oneida Lake, New York, reported upon by him in two very
interesting and valuable papers in 1916 and 1918. To these two papers
and to Dr. C. G. Joh. Petersen's several recent contributions on the valua-
tion of sea-bottom off the Danish coast (Reports of Danish Biological
Station, 1911-1918), I owe not a few ideas which have cast illumination
in more or less dark places. The general plan into which the present
piece of work is intended to fit, the directing force behind it, and the sup-
ply of means and general suggestions as to methods for its execution,
have been the work and care for many years of the Chief of the Natural
366
History Survey, Professor Forbes, without whose aid in these more pro-
foundly important respects the present investigation would doubtless
neither have been conceived or carried out in its present scope and form.
Illustrations of Apparatus. — Fig. 1. Iron dredge, showing canvas
protector • covering posterior bobinet bag, and forward coarse-mesh bag
hung backward inside.
Fig. 2. Iron dredge, showing canvas protector rolled back to un-
cover bobinet bag, and forward coarse-mesh bag pulled out in front of
frame.
Fig. 3. Ekman dredge, showing canvas protector covering pos-
terior bobinet bag, and forward coarse-mesh bag hung backward inside ;
front mud shoes of Ekman design omitted.
Fig. 4. Ekman dredge, disposed as iron dredge in Figure 2.
Fig. 5. Mud-dipper, showing bobinet bag pulled out in front of
thimble, and canvas protector in position for drag.
Fig. 6. Apparatus used in 1914 for collecting samples of the thin
bottom ooze for study of the composition of the lighter detritus and the
microorganisms entering into the food supply of the small bottom animals.
General Summary
It is the purpose of the studies here reported to make an estimate,
based on many quantitative collections, of the total store of animal life on
and in the bottom sediments of different sections of the middle and lower
Illinois River and its bottom-land lakes and on the plants of their shal-
lower, marginal waters, to trace the causes of the wide differences in this
respect between river and lakes and between different sections of the
stream, to estimate, also quantitativly, the food resources which the bottom
muds contain for the animals inhabitating them, and thus to trace in a gen-
eral way the successive steps by which the organic materials in the muds
and waters of the river system* are converted into forms available as food
for man. This is, in fact, to be regarded as essentially a soil survey of
these aquatic public properties, for the beds and weedy margins of rivers
and lakes are a natural soil of various fertility, of which the animals,
mainly univalve mollusks and a few kinds of insect larvae, are the crop,
harvested chiefly by fishes, these being harvested in turn by man. From
this point of view the upper Illinois River is, under present conditions,
mainly a mass of plant and animal weeds — forms which occupy the pol-
luted waters to the practical exclusion of everything useful to human
kind — but the current of this section carries elements of a normal fertility
to the lower reaches of the river, depositing a large part of them finally
in the silts and sediments of river and lake in forms available for the
nutrition of normal aquatic life, but bearing also an immense quantity
to the mouth of the stream where it escapes unutilized into the Mississippi.
The river system below Chillicothe varies enormously in the produc-
tiveness of its different parts, the richest of them being the weedy margins
367
368
369
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Fig. 5. Mud-dipper, showing- bobinet bag- pulled out in front of thimble,
and canvas protector in position for drag.
372
373
of the shallower lakes, and the poorest those sections of the river channel
which are swept comparatively bare of sediments by a relatively swift
flow. In the river itself much the most abundant product is found where
the current is most sluggish, and the bottom sediments are consequently
deepest and are most heavily charged with organic materials originally
washed into the stream by rains or poured into it by sewers of cities and
towns and transformed by oxidation into compounds suitable for the
nutrition of clean- water plants and animals.
In a stretch of the river above Havana, which, with its adjacent
lakes, is the richest part of the Illinois River system, the inshore and
bottom fauna of the lakes averages in weight to the acre about twice as
much as that of the river, and it is in the lakes that the fisheries give their
highest* yield. The bottom soils of the lakes are, indeed, richer in or-
ganic matter, as a rule, than are those of the river opposite, and the muds
of the marginal waters of these lakes are richer than those of their deeper
parts — facts traceable, in part, no doubt, to the more abundant light and
higher temperature of the shallower waters and the consequent greater
growth of plants whose decay enriches the soil from which they sprang.
At ordinary high-water levels the current of the river from Chilli-
cothe to the mouth varies from one to two miles per hour according to
the slope of the bottom, the width of the bed, and the presence or absence
of obstructions ; and at the highest water it does not much exceed three
miles per hour for any important distance. At ordinary midsummer levels
the current rate per hour varies in different sections from half a mile to
a mile. At lowest water it drops, between Chillicothe and the foot of
Peoria Lake, to as little as .29 mile per hour.
Above Havana the bottom, both along the shores and in the channel,
is, with some exceptions, a rather deep black mud, but below Havana
this shades gradually into hard clay or sand and shells, soft mud failing
completely in the channel for long distances. The quantity of inshore
vegetation is negligible in the river proper, even in the driest seasons,
since the opening of the sanitary canal of the Sanitary District of Chicago
in 1900. The bottom-land lakes between Copperas Creek and Lagrange
are gradually filling with river silt and a growth of plants. A few have
sandy beaches next the eastern bluffs, but the bottoms of all are otherwise
of deep black mud, mixed in the shallow water along shore with coarse
rotting vegetation. In midsummer the margins of all the deeper lakes,
to a depth of four to six feet, are well supplied with vegetation, while the
shallower lakes are in many cases weedy over their entire acreage.
From Chillicothe to Lagrange the animal life of both channel and
shore waters is almost wholly mollusks (86 to 99 per cent, in collections
made), but below Lagrange insect larvae (caddis-worms and May-fly
larvae) were more abundant than above in the shore muds, the ratio of
mollusks falling to 31 to 65 per cent. In the deeper, opener lakes, mol-
lusks made 77 to 96 per cent, of the collections, and in the shallower, more
weedy lakes, 36 to 79 per cent.
374
Speaking generally, the richest sections of the river floor are those
with the least average slope and the slowest current, and therefore with
the most abundant sediments. The quantity of the bottom fauna dimin-
ishes rapidly down-stream from Chillicothe, averaging 555 pounds to the
acre for the upper sixty miles (the weight of the shells of the mollusks
being in all cases deducted), 88 pounds for the forty-two and a half
miles next following, and 10.4 pounds for the lower seventy-seven miles.
The general average for the river channel from Chillicothe to the mouth
was 261 pounds per acre. That for Copperas Creek to Lagrange, within
which section lay the twelve principal lakes studied, was 705 pounds per
acre, and the highest sectional yield was 2,693 pounds per acre between
Copperas Creek and Havana. The highest local yield was found in the
lower half of this Copperas Creek-Havana section, whose channel prod-
uct rose to 5,196 pounds per acre. These enormous yields in the
stretch above Havana were evidently due, at least in great measure, to
the sluggish current and consequent heavy sedimentation and to the
great predominance (99 per cent.) of relatively large, thick-shelled snails,
edible only by the larger fishes, armed with a powerful crushing apparatus
in jaws and throat.
In the muddy section of river above Havana the channel yields ap-
proximated or even surpassed those of the shallow waters along shore;
but below Havana, where mud is largely replaced by sand, clay, or shells,
the channel yields were only 5 to 10 per cent, those of the longshore
zone.
Comparing river and lakes between Copperas Creek and Lagrange
(59.3 miles) we find that the average bottom yield per acre of twelve
lakes examined was about one third that of the river opposite them,
but that it was practically the same as the average for the entire river
from Chillicothe to the mouth. The deeper lakes with sandy beaches at
one side yielded about twice as much per acre as the shallower lakes with
mud banks all around.
In the deeper bottom-land lakes surrounded by mud banks, the shore
belt, to a depth not exceeding six feet, yielded about three times as much
bottom fauna per acre as the deeper open water of these lakes ; but in
the sand-beach lakes this relation was reversed, the deeper bottom yield-
ing five or six times as much as that within the 6-foot line.
The foregoing statements all apply to the animals living in or on
the bottom muds ; but in the shallow, weedy areas of lakes and back-
waters the small invertebrate animals living on and among the weeds
greatly exceed both in number and in weight per acre the fauna of the
bottom itself, aggregating in many collections made near Havana in 1914,
from 1,100, to nearly 2,600 pounds per acre, with an average of 2,118
pounds — quantities to be compared with an average of 255 pounds of
bottom fauna per acre from the lakes of the same district.
Combining weed and bottom faunas of our collections and applying
their joint averages to the entire area of lake and backwater between
375
Copperas Creek and Havana, we get a yield of 1,447 pounds per acre, to
be compared with 705 pounds per acre for the unusually rich sections of
the river opposite.
From analyses of the bottom muds of the river channel and esti-
mates of the nitrogen content of total bottom fauna per acre, it appears
that the nitrogen in the river sediments is many hundred times the nitro-
gen content of the flesh of the animals living in them, and that the total
dry organic matter in the channel muds is several thousand times the
dry weight of this bottom fauna.
Chemical analyses show that the bottom soils of the lakes are richer
in organic matter than those of the river opposite them, and that in the
lakes themselves the bottom soil is richer near the shore than at the center.
The plankton of the river passing Havana in a year amounts to about
200,000 tons live weight, equivalent to four thousand to ten thousand
tons dry weight. This is, roughly, 20 to 50 times the total dry weight of
the flesh of the animals of the bottom muds of the lakes from Copperas
Creek to the mo'uth, a distance of 138 miles.
An estimated total of 600,000 tons dry weight of organic matter,
suspended and dissolved, passed Chillicothe in 1914. This is 60 to 150
times the dry weight of the plankton that passed Havana in twelve
months (1909 and '10), and 3,000 times the dry weight of the total bot-
tom fauna of 1915 from Copperas Creek to the mouth of the river.
The dry weight of nitrogen in the above organic matter was sufficient to
replace the nitrogen in the plankton of a year from 92 to 232 times.
The plankton per cubic meter of water was greater throughout the
year in Thompson Lake than in the river opposite in 1909 and '10, the
difference being greatest at times of lowest production (midsummer and
winter) in both river and lake.
The river plankton is constantly settling to the bottom to an impor-
tant degree, as is shown by the composition of the bottom ooze and by
the stomach contents of small invertebrates living on and in it. In June,
1914, living, moribund, or recently dead limnetic plankton was more
abundant in the upper layers of the ooze than the normal bottom plank-
ton or old organic detritus, as was shown by the food of Sphaeriidae,
Trichoptera, and Chironomidae, and it made also an important part of
the food of large detritus-eating gastropods (Viviparidae, Pleuroceridae,
etc.).
There is a much greater loss of plankton down-stream than can be
explained by dilution merely. The falling off in plankton, per cubic
meter between Havana and Grafton amounted, during nine months of
the growing season, to approximately 62 per cent., notwithstanding the
normal rate of multiplication of the planktonts as they passed down
stream. These losses were greatest when the current was slowest and
settling consequently easiest. They were not due to lack of food, because
the percentage of nitrogen and the nitrates increased from Havana down-
ward.
376
In our opinion and that of the most intelligent and observant fisher-
men, the lakes are the favorite feeding grounds of the larger and more,
common fishes, and this opinion is supported by the fact that the lakes
have a more abundant food supply per acre than the river, and that the
heaviest fish-yields come from sections where the ratio of lake areas to
river is greatest.
The average weights of the yields of the inshore bottoms of the
Illinois River lakes in 1915 were about five times as great per acre as
those of the glacial lakes of northeastern Illinois in 1916, and the com-
position of the faunas was also widely different, mollusks occurring in
the latter in relatively insignificant proportion and being nearly all of
the smaller species. The weed faunas of Fox and Pistakee lakes were
almost wholly made up of small crustaceans and insects, the former
predominating, although the total weights were not very much less than
those of the Illinois system.
Hydrography and Bottom Fauna, Illinois River,
Chillicothe to Grafton, July-October, 1915
(a) Chillicothe to Foot of Peoria Lake (18.5 Miles)
Hydrography. — If the Illinois River is a sluggish stream considered
as a whole, in comparison with most other important American rivers,
the grand prize for local leisureliness of movement belongs to the short
stretch between Chillicothe and the lower end of Peoria Lake, where,
in March, 1903, at a Hood, stage of approximately eighteen feet above
old low-water marks at Peoria, it took ball floats twenty-nine hours and
fifty-nine minutes to make a total distance of 17.7 miles, the average rate
per minute being 51.94 feet, and per hour, 0.59 mile. At a gage of nine
feet, Peoria, which is almost exactly the mean level of the month of
August, 1914, and represents the lowest water in this part of the river
in the past seven years, these rates would be reduced to 25.97 feet per
minute or 0.29 mile per hour — a total time in transit of fifty-nine hours
and fifty-eight minutes for the 17.7 miles.
These velocities compare with an average of 229.47 feet per minute
or 2.60 miles per hour at a corresponding flood gage for the 33.9 miles
Morris — Utica; and with 115.43 feet per minute or 1.31 miles per hour
for the 229.6 miles between Utica and Grafton. Above Peoria only
the 12-mile section Henry — Hennepin has a current approaching the low
figures fouiid between Chillicothe and Peoria. In the other short reaches
above Peoria, and in all below Peoria except the section of 8 miles between
Liverpool and Havana (with 66.00 feet per minute, or 0.75 mile per
hour), average flood velocities are over 100 feet per minute (1 mile per
hour). The greatest velocities below Utica occur in the 9.8 miles between
Peoria and Pekin (with 191.64 feet per minute or 2.17 miles per hour) ;
and in the reaches below Florence, which have over 180 feet per minute,
or more than 2 miles per hour.
377
Table of Approximate Average Velocities, Illinois River
This table is based on float records of J. L. Van Ornum, as published in
Water Supply Paper No. 194, U. 8. Geological Survey, 1007, pp. 17-18.
(The gage at Peoria averaged about eighteen feet during the tests. The
figures for nine feet are one half the 18-foot figures, various measurements by
the U. S. Geological Survey and others showing about 50 per cent, decrease in
velocity betiveen approximately these gages at Peoria and corresponding gages
at other stations.)
Reach
Gage, 18 ft., Peoria
Ft. per min. Mi. per hour
Gage, 9 ft., Peoria
Ft. per min. Mi. per hour
Morris to Utica
Utica to Grafton
Utica to Hennepin
Hennepin to Henry
Henry to Chillicothe. . . .
Chillicothe to foot Main
St., Peoria
Foot Main St., Peoria, to
Pekin
Pekin to Banner*
Banner to Liverpool....
Liverpool to Havana ....
Havana to Beardstown. .
Beardstown to Lagrange
dam
Lagrange to Florence . . .
Florence to Kampsville
dam
Kampsville dam to Graf-
ton
33.9
229.6
229.47
115.43
2.60
1.31
114.73
57.61
1.30
0.65
21.6
12.0
15.5
17.7
9.8
14.3
10.7
8.0
31.5
11.0
21.9
24.2
31.4
137.73
67.33
103.98
51.94
191.64
114.40
105.01
66.00
129.13
152.04
146.92
183.85
186.91
1.56
0.76
1.18
0.59
2.17
1.30
1.19
0.75
1.46
1.72
1.66
2.08
2.12
68.86
33.66
51.99
25.97
95.82
57.20
52.50
33.00
64.56
76.02
73.47
91.92
93.45
0.78
0.38
0.59
0.29
1.08
0.65
0.59
0.37
0.73
0.86
0.83
1.04
1.06
Differences in velocity within the 18 miles between Chillicothe and
Peoria are indirectly shown in the next table in figures for elevation of
water surface at the low gage of 1901. In more than thirteen out of
the eighteen miles the decline was too small to be measured; for one-
half mile there was an average slope of over two inches ; and in the
lower four and a half miles a slope of about three fourths of an inch
per mile.
Widths between banks in this section of the river at the low water
of 1901 ranged from 439 feet just below Chillicothe to more than a mile
in the widest parts of the expanded portion known as Peoria Lake,
which occupies more than seventeen of the eighteen and a half miles.
If we figure the normal area of the river proper per mile throughout the
reach at the 1901 low water at a mean (80.0 acres per mile) between the
* About 2 miles above Copperas Creek dam.
378
Decline in Elevation of Low-Water Surface, 1901
Reach
Interval
miles
Av. slope
(inches)
per mile
Chillicothe-
—foot Peoria Lake
18.3
0.26
Chillicothe
(mile 180.5)— Mile 171.0*
9.5
Not meas-
urable
Mile 171.0-
-170.5
0.5
2.40
Mile 170.5-
-166.9
3.6
Not meas-
urable
Mile 166.9-
-165.5
1.4
0.85
Mile 165.5-
-163.8
1.7
0.70
Mile 163.8-
-162.2 (foot of lake)
1.6
0.75
averages just above and just below Peoria Lake, this is found to be less
than one fourth of the actual average continuous area flooded in each
mile (379.9 acres) ; or, in other words, the river was on the average
throughout this eighteen-mile section at those levels more than four times
normal width. The ex-river or lake acreage per mile at the low water
of 1901 figured in this way (379.9 — 80.0=299.9 acres per mile) in fact
exceeded that found for any other sections of the river except two, viz.,
the 16.8 miles between Copperas Creek dam and Havana and the 42.5
miles between Havana and the Lagrange dam.
Lake and Pond Acreage, Low Water, 1901
(as in valley before levees)
Lake and
TLeaoh.
Interval
pond
miles
acreage
per mile
Chillicothe to foot Peoria Lake
18.5
299.9
Foot Peoria Lake to Pekin
9.0
113.6
Pekin to Copperas Creek dam
16.2
219.0
Copperas Creek dam to Havana
16.8
472.1
Havana to Lagrange dam
42.5
382.4
Lagrange dam to Florence
21.9
219.6
Florence to Kampsville dam
24.2
180.0
Kampsville dam to Grafton
31.4
86.9
Depths in the river channel between Chillicothe and the foot of
Chillicothe Island (0.9 mile below Chillicothe, the point where the ex-
pansion into the wide waters of Peoria Lake begins) were 22.5 to 24 feet
at the low water of 1901, and have been about four and a half feet more
than those figures at recent low gages. The channel through the lake at
the low water of 1901 varied in depth from about seven to a little over
twenty feet; and at recent low levels from over eleven to over twenty-
four feet.
* Mile figures represent miles above Grafton.
379
Widths and Depths, Chiixicothe to Foot of Peoria Lake,
Low Water, 1901
Miles above Qf .. „ 1 Width, 1 DePth'
Grafton ft. _, JL
1 | 1 max.
180.2
179.6
Unwidened river —
500 yds. below boat-landing, Chillicothe
Foot Chillicothe Island
494
439
24.0
22.5
178.4
177.9
175.5
Upper lake —
Head Peoria Lake, one half mile above Rome
Rome
One and a half miles above Spring Bay
1,000
3,960
5,463
17.0
14.0
7.5
Middle lake —
173.4
500 yds. below Spring Bay
1,024
10.8
173.1
About half a mile below Spring Bay
1,850
16.8
169.5
Three miles above Peoria Narrows
5,627
10.0
168.0
One and a half miles above Peoria Narrows
5,280
20.1
Lower lake —
166.5
Peoria Narrows (above bridge)
658
15.5
164.2
Opposite work-house
3,922
12.5
162.5
Opposite foot Main St.
1,760
10.8
162.2
Lower wagon-bridge
870
5.1
As we should expect, the upper soil strata in the channel through-
out most of this section consist of dark-colored mud of a good depth.
The mud layer is four feet deep in the channel at Chillicothe, and ranges
from 7.5 to over 22 feet in depth at boring stations (U. S. Engineers,
1902-05) in the upper, middle, and lower lakes, if we except a stretch
of less than two miles in and immediately below Peoria Narrows. At
the Narrows and just below, cap-rock comes to within four or five feet
of the surface, and the upper stratum consists of a well-packed, mix-
ture of mud and shells. This is followed for about a mile by a deep
upper layer of dirty sand and shells, after which (between Mile 165 and
Mile 164)' deep mud begins again and is continued to the foot of the lake.
At the foot of the lake rock comes again to within eight feet of the sur-
face, and the floor of the river just above the mouth of Farm Creek is
formed by gravel fifteen feet deep — hard bottom of sand or sand and
shells continuing from this point all the way to Pekin.
Findings regarding bottom deposits at our collecting stations in
1915 agree very well, as far as they go, with the data from the government
borings, and are satisfactorily consistent with such data as we have on
slope and velocity. The mud brought up by the dredges, except at Pe-
oria Narrows, was all very dark in color, and the recent origin of much
of it was indicated by the softness of the upper layers. Measurements
380
of the "depth to hard bottom"* ran from thirty-six to seventy-two
inches at stations between Rome and the foot of Main St., Peoria. At
the Narrows the mud was harder, lighter in color, and was mixed with
old dead shells and thickly carpeted with sponges and Bryozoa.
Depth (of Softer Mud) to Hard Bottom at Channel Stations
Miles above
Grafton
Station
Inches
180.5
177.2
175.5
172.3
166.5
162.7
Chillicothe
One mile below Rome
Peoria Narrows
Opposite Mossville
One and a half miles above Spring Bay
Opposite foot Main St.
3
72
Hard bottom
48
36
36
The elevation of the bottom of the river channel eighteen miles south
of Chillicothe, instead of being lower, is actually more than eighteen feet
higher than the plane of greatest depth opposite Chillicothe ; more than
fourteen feet above the bottom^ plane of the deepest part of Peoria Lake
above the Narrows ; and more than two feet higher than the highest
point in the channel bottom between Chillicothe and the foot of the lake.
I think we must suppose that the way out of Peoria Lake was once much
more open, and that the action of Farm Creek has been largely re-
sponsible for building up the high bar that now dams up the entrance
into the Pekin reach. The nearness to the surface of rock between Pe-
oria Narrows and Wesley would, however, have prevented in any case
the excavation of a fast and deep channel through the Chillicothe-Pe-
oria section.
Because of the very shallow gradient, and the great expansion of
the river between Chillicothe and Peoria, the shallower backwater in
most of the distance, though not separable from the river channel by
any distinct boundary, resembles more nearly the larger inclosed bottom-
land lakes than ordinary river littoral. Except for a very short distance
at and near Peoria Narrows, the land to the eastward of the channel is
low, the banks are all of mud, and the soft bottom sediments very dark
in color. Within the 3- foot line on this side the bottom muds contain
more decayed vegetable matter than further out, and there is a good
deal of living vegetation (principally Potamogetons and Ceratophyllum)
during the dry season. On the west side of the channel, sand or gravel
or hard mud bottom is. found for considerable distances out to a depth
of three to seven feet wherever the channel closely approaches the blufT.
Opposite Mossville, where the channel is east of the middle of the lake,
the 1-3- and 4-7-foot zones on the west side are very similar in mid-
summer to those on the east side first described. Except for a short dis-
* Made by forcing- a 2 X 2-inch pole, square across the end, as deeply into
the mud as a strong man could with both hands.
381
tance at this place, such vegetation as grows on the west side is usually
only a thin fringe next the rather steep bank. Outside the 4-foot line
Peoria Lake has recently been almost entirely free of vegetation, even
at the lowest gages, and it is consequently much more subject to roiling
by winds than the narrower and weedier lakes near Havana.
The Bottom Fauna. — Collections of the small bottom animals, with
dredges and mud-dipper, were made in the channel July 26 to August
19, 1915, at four stations in the mud-section between Chillicothe and
Peoria Narrows ; in the hard mud at Peoria Narrows ; and in the mud
opposite the steamboat landing at Peoria.
Channel Collections, Chillicothe to Peoria Lake, 1915
Miles
above
Grafton
Station
No. col-
lections
July —
August,
1915
Depth ad-
justed to
gage
July —
October,
1910—1914
180.5
Chillicothe
2
28
Deep, narrow river
177.2
175.5
One mile below Rome
One and a half miles
above Spring Bay
1
3
12
11
Upper lake, channel
172.3
Opposite Mossville
2*
19
Middle lake, channel
166.5
Peoria Narrows
3
19
162.7
Opposite Eagle Packet
landing
4
15
Lower lake, channel
Total channel collections,
15
The average number of bottom animals in a square yard of channel
bottom, if we except the Peoria Narrows station (which represents a
very limited area with hard bottom), compared favorably (at 235 per
sq. yd.) with the figures from some other short reaches between Peoria
and Havana, but was under the average for the 60.5 miles (416 per sq.
yd.), and was far below the figure for the very rich section of eight
miles just above Havana (1,469 per sq. yd.). In all the collections Mol-
lusca (Gastropoda and Sphaeriidae) were much more numerous than
insects, worms, and small Crustacea; and the larger Gastropoda (Vivi-
paridae and Pleuroceridae) were usually more abundant than the
Sphaeriidae and smaller Gastropoda (Amnicolidae, etc.).
382
Bottom Fauna, Channel, 1915
numbees per square yard, average
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Col-
lec-
tions
Chillicothe — Mossville
At Peoria Narrows
Peoria Narrows to foot of
Peoria Lake
88.2
23.2
134.5
143.7
1.0
5.0
26.6
13.3
48.0
258.5
37.5
187.5
8
3
4
Average (excepting collec-
tions at Narrows)
234.8
12
The average valuation of the channel bottom fauna in pounds per
acre (shells of Mollusca deducted) in this section (285.9 pounds, with
the Peoria Narrows station included ; 345.1 pounds, with Peoria Nar-
rows omitted) was better than the average (239 pounds) for the 43.7
miles between Chillicothe and the Copperas Creek dam, but was less
than one tenth of the channel average between Copperas Creek dam and
Havana (3,029 pounds per acre), and less than one twentieth of the
average valuation for the eight miles between Liverpool and Havana in
1915 (5,180 pounds per acre). The great bulk of the collections, by
weight (85 per cent.), was made up of the larger snails (Viviparidae and
Pleuroceridae), and these families together with the Sphaeriidae and
smaller Gastropoda accounted for about 98 per cent, of the average
poundage taken.
Bottom Fauna, Channel, 1915
pounds per acre, average
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Col-
lec-
tions
Chillicothe to Mossville
At Peoria Narrows
Peoria Narrows to foot of
Peoria Lake
244.1
46.3
391.6
70.4
0.5
3.1
3.1
2.1
5.6
317.6
48.9
400.3
8
3
4
Average (including Nar-
rows)
Per cent, of total
243.8
85.2
38.4
13.4
3.5
1.4
285.9
15
Average (excluding Nar-
rows)
Per cent, of total
293.2
84.9
47.8
14.0
3.9
1.1
345.1
12
383
A total of thirty collections in the shallower areas between Chilli-
cothe and the foot of Peoria Lake were taken with the mud-dipper in
1915; ten within the 4-foot line, and twenty between the 4- and 7-foot
lines (depths adjusted to gage July-October, 1910-1914).
Shore Collections, Chlllicothe to Foot of Peoria Lake, 1915
Miles above
Station
1- to 3-foot
zone
4- to 7-foot
zone
Grafton
Collections
Collections
180.5
177.2
175.5
172.3
162.7
Chillicothe
One mile below Rome
One and a half miles above
Spring Bay
Opposite Mossville
Opposite Eagle Packet Landing
3
2
4
1
2
5
5
4
4
Total collections
10
20
Average numbers per square yard in the 1- to 3-foot zone (233.7)
were about the same as in the channel opposite (234.8), but were appre-
ciably under those found in the 4- to 7-foot zone (314.6). Both in
the 1- to 3-foot and the 4- to 7-foot zones there were proportionally much
larger numbers of Sphaeriidae and of insects, worms, and small Crus-
tacea than were present in corresponding channel collections.
Bottom Fauna
1- to 3-foot Zone, 1915
numbers per square yard, average
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Col-
lec-
tions
Chillicothe to Mossville
Peoria Narrows to foot of
Peoria Lake
7.7
50.0
148.6
70.0
76.3
120.0
232.6
240.0
9
1
Average
236.3
10
The average poundage per acre of bottom animals in the 1- to 3-foot
zone* (108.4 pounds) was less than one third the average channel valua-
* No collections at Peoria Narrows.
384
4- to 7-foot Zone, 1915
numbers per square yard, average
Chillicothe to Mossville
Peoria Narrows to foot of
Peoria Lake
30.8
53.0
200.3
167.5
68.7
52.5
299.8
373.5
16
4
Average
314.4
20
tion opposite (345.1 pounds), although numbers per unit area were about
the same, the Sphaeriidae and smaller Gastropoda making up over 50
/per cent, of the average in weight and the insect larvae, worms, and
Crustacea over 7 per cent, as compared with much smaller ratios in the
channel collections.
The average 4- to 7-foot zone* valuation (259.4 pounds per acre)
was about two and a half times that of the 1- to 3-foot zone (108.4
pounds), and about 25 per cent, under the average channel valuation
(345.1 pounds). The larger snails (Viviparidae principally), while not
relatively so abundant as in the channel collections, made up a noticeably
larger portion (64.6 per cent.) of the totals by weight than was the case
in the 1- to 3-foot zone.
Tables summarizing these comparisons of the channel and shore
zone averages follow. Further details concerning separate species and
families included in the valuations are found in the detailed tables at end.
Bottom Fauna, Chillicothe to Foot of Peoria Lake,* 1915
Summary
Channel,
12
collections
4- to 7-foot
zone, 20
collections
1- to 3-foot
zone, 10
collections
Average number per square yard
Average pounds per acre
234.8
345.1
314.6
259.4
233.7
108.4
Per cent, (by weight)
Viviparidae and Pleuroceridae
Per cent, (by weight)
Sphaeriidae and small Gastropoda
Per cent, (by weight)
Insects, worms, Crustacea
84.9
14.0
1.1
64.6
30.9
4.5
41.3
51.6
7.1
* No collections at Peoria Narrows.
* Channel collections at Peoria Narrows omitted.
to 3-foot or 4- to 7-foot zone at that station.
No collections taken in 1
385
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386
(b) Foot of Peoria Lake to Pekin (9 Miles)
Hydrography. — After- passing over the high bar above the mouth
of Farm Creek (foot of Peoria Lake) the river follows a comparatively
swift and narrow channel to Pekin, the average velocity at a flood gage
of eighteen feet, Peoria, being 191.64* feet per minute for the 9.8 miles
between the foot of Main St. and the wagon bridge at Pekin, and the
width (at low water of 1901) usually under six hundred feet. The aver-
age slope of the water surface at the low levels of 1901 was two inches
per mile, and 4.36 inches per mile at the high water of March, 1904.
These average slopes and velocities are much greater than are met with
in any other considerable section of channel in the one hundred and
twenty-five miles between Chillicothe and Florence, and are four to
seven times the figures for the 18.5 miles between Chillicothe and the
foot of Peoria Lake.
Decline in Elevation of Water Surface
Reach
Stage of
river
Interval
miles
Av. slope
inches
per mile
Low water
Foot of Peoria Lake to Pekin
1901
Flood stage
9.2
. 2.00
(<
Mar. 15, 1903
9.2
3.45
Flood stage
it
Mar. 31, 1904
Low water
9.2
4.36
Chillicothe to foot Peoria Lake
1901
Flood stage
18.3
0.26
<<
Mar. 31, 1904
18.3
0.64
The channel floor is sand and shells, nearly denuded of mud, for
most of the nine miles. At our 1915 collecting stations between Wesley
and Pekin the bottom was hard, but opposite Pekin the hard bottom was
overlaid with a very thin covering of soft silt. Between the 4- and 7-
foot lines at Wesley in 1915 hard gravel bottom washed clean of mud
was found both on the east and west sides. At the shore stations below
the wagon bridge at Pekin six inches of soft mud was found on the west
side and 12 to 36 inches on the east. Shore vegetation, except an occa-
sional narrow fringe at the bank edge, is wanting.
At the low water of 1901 the bank to bank width of the river be-
tween Peoria and Pekin was usually between 400 and 600 feet, only
a very short stretch just below the mouth of Farm Creek much exceed-
ing 600. Depths in the wider and shallower stretches ranged from 7
to %y2 feet; and in the deeper and narrower ones between 10 and 13 feet.
Average depths at recent low levels (gage of July-October, 1910-1914)
have been about 3^ feet more than these figures. The connecting lake
* Table, p. 377.
387
acreage (113.6 acres per mile at the low water of 1901) is little more
than a third of that which occurs between Chillicothe and the foot of
Peoria Lake (299.9 acres per mile) ; and is under the rating of any other
section of the river between Chillicothe and Kampsville.*
Widths and Depths, Foot of Peoria Lake to Pekin, Low Water, 1901
Miles above Grafton
Station
Width, ft.
Depth ft.
max.
161.9
160.7
159.9
159.0
158 0
50 yds. below mouth Farm Cr.
P. &. P. U. R. R. bridge
100 yds. below Wesley
347
915
640
402
514
586
640
515
439
475
8.1
6.6
11.8
8.3
7 5
157.0
7 5
156.0
7 2
155 0
8 5
153 9
12 4
153 3
10 3
153.0
Pekin, at wagon bridge
11.2
Bottom Fauna. — The bottom collections made in cross-sections at
Wesley and Pekin in 1915 included four channel hauls and four hauls
in the 4r-7-foot zone. In neither depth zone was a fauna indicated quite
so rich as that of the channel and shore zones between Peoria and Chilli-
cothe, the average channel poundage amounting to 253.8 lbs. per acre, and
that of the 4-7-foot zones to only 206.3 lbs.
Larvae of caddis-flies (principally Hydropsyche sp.) were decidedly
more abundant in the swifter stretches of channel between Peoria and
Bottom Fauna, Channel, Wesley to Pekin, 1915
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Number per sq. yard,
Average
87.7
16.7
129.0
Pounds per acre, av.
224.6
8.3
20.9
Total
233.4
253.8
collec-
tions
4 collec-
tions
Per cent, of total,
(By weight)
88.6%
3.2%
8.2%
* See table, p. 378.
388
Pekin than above Peoria, and the Sphaeriidae less sp. The larger Gas-
tropoda (Viviparidae and Pleuroceridae) made up about the same per-
centage of the average weight of collections as above Peoria (88.6%).
In the 4-7-foot zone the Sphaeriidae showed the heaviest poundages
(66.2% of totals), and the insect larvae and the larger snails were rela-
tively much less abundant than in channel collections.
Bottom Fauna, 4 — 7-foot Zone, Wesley to Pekin, 1915, Average
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Number per sq. yard
20.0
272.5
56.5
349.0
4 collec-
tions
Pounds per acre
60.0
136.7
9.6
206.3
4 collec-
tions
Per cent, of total,
(By weight)
29.2%
66.2%
4.6%
(c) Pekin to Copperas Creek Dam (16.2 Miles)
Hydrography. — Following the swift run from the foot of Peoria
Lake to Pekin, where the low-water slope in 1901 was 2.00 inches per
mile, the effect of the dam at Copperas Creek became very distinct be-
low Pekin at those low levels, and the average slope of water surface
between Pekin and the dam fell to 0.14 inch per mile. Although this
average low-water decline is not much more than half that between
Chillicothe and the foot of Peoria Lake (0.26 inch per mile for 18.2
miles), at ordinary spring flood-levels the slope rate is multiplied ten
times or more (1.40 inches per mile at gage 18 ft., Peoria), and the aver-
age flood velocity (114.40 feet per minute at gage 18 ft., Peoria) rises to
a figure more than double that between Chillicothe and Peoria.*
This circumstance — a consequence of the fact that at flood stages the
sweep of the current tends to follow the old lines of slope of water sur-
face as they existed before the low-crested dam was put in — accounts
for the generally well-scoured channel floor that we find throughout this
reach of 16.2 miles, not even excepting its lowermost portion just above
the dam.
The only important stretch of soft mud bottom in the channel in
the 16 miles is the deposit occupying less than a mile of channel length
just above the mouth of the Mackinaw. With the exception of that and
of about a mile of dirty sand which ends a mile above the dam, the gov-
* Table, p. 377.
389
Decline in Elevation of Water Surface
Reach
Stage of river
Interval
miles
Av. slope
inches per
mile
Pekin to Copperas Creek dam
(above)
Low water
- 1901
16.2
0.14
Pekin to Copperas Creek dam
(above)
Flood stage
Mar. 15, 1903
16.2
1.36
Pekin to Copperas Creek dam
(above)
Flood stage
Mar. 31, 1904
16.2
1.43
ernment borings of 1902-1905 showed hard bottom at all channel sta-
tions, the upper layer of sand, gravel, or sand and shells having depths
of from five to twenty-nine feet. In the shore zones within the 7-foot
line mud bottom was found by us in 1915 at all the collecting stations.
There is no shore vegetation worth mentioning in the 16 miles.
Between Pekin and Copperas Creek dam at the 1901 low levels,
bank to bank widths averaged rather greater than in the Peoria-Pekin
section, being usually over 600 feet, and for short distances 700 feet and
over. The greatest depths at these levels were under 15 feet, and in a
Widths and Depths, Pekin to Copperas Creek Dam,
Low Water, 1901
Miles
above
Grafton
Station
Width, ft.
Depth, ft.
max.
153.0
152.8
Pekin at wagon bridge
695
•
750
440
677
384
600
610
695
700
549
732
622
586
530
550
586
570
677
549
11.2
13.0
152.5
7.1
151.7
10.2
150.5
11.0
149.9
8.6
149.3
14.1
149.0
9.0
147.9
12.6
146.8
7.4
145.6
145.2
8.7
14.7
144.6
7.0
143.9
8.4
142.9
8.3
141.3
11.6
139.0
8.4
138.3
14.5
137.7
9.3
137.2
10.4
136 95
11.0
136.8
Dam
390
large part of the section ranged between 7 and 9 feet. Recent maximum
low-water depths have been mostly 2 to 3^ feet more than these. The
connecting lake and pond acreage in this section at the low levels of 1901
(219.0 acres per mile) was about twice that between Peoria and Pekin
per mile of river length, but was not much more than two thirds that
between Chillicothe and the foot of Peoria Lake, and was less than half
that between Copperas dam and Havana.*
Bottom Fauna. — A total of 14 channel collections and 16 shore col-
lections were made between Pekin and the dam in 1915 at stations as
shown below.
Miles
above
Grafton
Station
•
Channel
4 — 7— ft. zone
1 — 3-ft. zone
151.5
iy2 miles below Pekin
2
2
145.6
Opposite Kingston
6
3
3
141.9
Opposite Spring Lake canal
4
4
4
136.8
100 yards above dam
2
Total
14
The average valuation figure for the channel fauna in the section
(144.8 lbs. per acre) was lower than in any other important stretch of
channel between Chillicothe and Havana. The weight of the average
channel collection was not far from equally divided between the
Sphaeriidae and the larger Gastropoda, the first contributing 43.7%, the
Bottom Fauna, Channel, Pekin to Copperas Creek Dam, 1915
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Number per sq. yard,
Average
28.8
126.9
49.8
205.5
14 collec-
tions
Pounds per acre,
Average
73.3
63.4
8.1
144.8
14 collec-
tions
Per cent, of total,
(By weight)
50.6%
43.7%
5.7%
* Table, p. 378.
391
latter 50.6%. The insects, worms, and small Crustacea made up the re-
maining 5.7%, the greater part of which was composed of the larvae
of the commoner channel caddis-flies.
In the shore zones both numbers and weight valuations were con-
spicuously higher than in the channel, the average poundage in the
4-7-foot zone being 695 per acre and that in the 1-3-foot zone 391. Con-
trary to the rule found usually to hold good in the river, the larger Gas-
tropoda (Viviparidae principally) here showed larger poundages and
much larger percentages of valuation totals (74 to 91%) both in the
1-3- and 4-7-foot zones than did the Sphaeriidae. The insects, worms,
and Crustacea contributed less than one per cent, of the average pound-
age figures in the 4-7-foot zone. In the hauls taken inside the four-foot
line, leeches and chironomid larvae were especially abundant, and these
with a few worms and small Crustacea added, made up over 8% of
the weight of the average haul.
Bottom Fauna, 4 — 7-ft. Zone, Pekin to Copperas Creek Dam, 1915
Viviparidae
and
Pleuroceridae
■ Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Number per sq. yard,
Average
177.6
104.0
34.4
316.0
9 collec-
tions
Pounds per acre,
Average
638.0 ■
52.4
5.1
695.5
9 collec-
tions
Per cent, of total,
(By weight)
91.7%
7.5%
0.8%
Bottom Fauna, 1 — 3-ft. Zone, Pekin to Copperas Creek Dam, 1915
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Number per sq. yard,
Average
108.4
135.7
116.8
360.9
Pounds per acre,
Average
292.4
67.8
31.2
391.4
Per cent, of total,
(By weight)
74.7%
17.0%
8.3%
392
(d) Copperas Creek Dam to Havana (16.8 Miles)
Hydrography. — One is at first surprised to find that although at
the low water of 1901 there was a decidedly greater decline in elevation
of water surface between the foot of the dam at Copperas Creek and
Havana (o.j8 inch per mile for 16.8 miles) than between Pekin and
the head of the dam (0.14 inch per mile for 16.2 miles), average flood
velocities in the section below the dam are less than in the section of
similar length above it. The average velocity at a gage of 18 feet,
Peoria, March, 1903, was 83.81 feet per minute between Banner — about
2 miles above the dam — and Havana; and was 114.40 feet per minute
between Pekin and Banner. The average slope of high water surface,
however, is in close correspondence with these flood velocities — equal-
ing 1.43 inches per mile between Pekin and the dam, as compared with
1.18 inches per mile between the dam and Havana at a gage of 22.6 feet,
Peoria, March 31, 1904 ; and 1.36 inches per mile between Pekin and
the dam, compared with 1.11 inches between the dam and Havana at a
gage of 19.0 feet in March, 1903. As the low flood velocities through
Peoria Lake are a joint consequence of the high bar above the mouth
of Farm Creek and the unusual opportunity for expansion in the broad
and low flats above it, the retardation of the flood current between Cop-
peras Creek dam and Havana may be explained also as due jointly to
the increased impounding area in this section* and to the high mud bar,
superimposed upon an older sand bar, which attains its summit about a
mile above the mouth of Spoon River. The top of this bar has an
elevation only 0.6 foot below the level of the channel floor just below the
dam at Copperas Creek, and is 13.8 feet higher than the deepest part of
the channel between Liverpool and Havana. The artificial pool behind
the dam at Copperas Creek, on the other hand, lies toward the lower
end of a stretch of river with relatively steep natural slope, and at the
higher gages the flood water moving through that section tends to follow
the old slope-lines of water surface as they existed in the years antedat-
ing the construction of the dam.
Quite consistently with what has just been noted, both at flood
stages and at the 1901 low levels, average slope and current are ap-
preciably greater in the first than in the second half of the 16.8 miles be-
low the dam, the average velocity (66.00 feet per minute) in the eight
miles immediately above the Havana bar at a flood gage of 18 feet,
Peoria, being in fact not much more than half that in the first eight miles
(105.01 feet) and less than that of any other considerable reach of
channel in the whole river below Peoria.
In the first seven miles of channel below Copperas Creek dam the
upper bottom stratum as shown by the government borings of 1902-1905
was sand and shells or plain sand to a depth of 4 to 21 feet for the
greater part of the distance; though dirty sand or sand and shells oc-
curred .at a few of the boring stations and was found by us just above
* Table, p. 378.
393
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394
and just below Senate Island in 1915. In the nine miles of deeper chan-
nel between Mile 129 (1 mile above Liverpool) and Havana, the bottom
is uniformly mud. The depth of the mud layer is nearly everywhere
more than 8 feet, and in extreme instances 13 to 17 feet. The thickness
of the mud stratum diminishes to about 7 feet opposite Havana, and a
quarter mile farther south the mud quite gives way to a layer of mud
and shells, which description of bottom continues nearly uninterrupted
for the next 14 or 15 miles. The bottom soils found in the shore zones
between Havana and Copperas Creek in 1915 were dark-colored soft
mud throughout the 16.8 miles.
Between the dam and Liverpool, bank to bank widths at the low
water of 1901 were much as between Pekin and Copperas Creek —
usually 550 to around 700 feet ; while the greatest depths were under 12
feet. Below Liverpool the river narrows and deepens decidedly, as far
as Mile 122.4 — the beginning of the expansion formerly known as
Havana Lake. In this six miles, widths at the 1901 low levels ranged
from 329 to about 500 feet, and depths from 14 to 21 feet. Opposite
Havana, for a distance less than half a mile above the mouth of Spoon
River, the wide water spread over the Havana bar (Havana Lake)
showed an extreme width in the summer of 1901 of about 1,300 feet;
while maximum channel depths in the 3 miles above Mile 121 (1 mile
above Havana) tapered off southward from more than sixteen to about
seven feet. Recent extreme depths at midsummer low gages in the
lower half of this reach have ranged from 4 to 5 feet more than the
low-water depths given.
Widths and Depths, Copperas Creek Dam to Havana, Low Water, 1901
Miles
above
Grafton
Station
Width, ft. "
Depth, ft.
max.
136.6
136.0
500 yards below dam
677
695
475
586
549
603
586
528
439
439
402
340
329
457
475
586
1,299
514
7.5
7 7
134.3
8 6
133.0
8 3
132.5
129.8
1 mile below foot Senate Island
11.8
10 0
129.0
128.5
1 mile above Liverpool
10.8
11 6
128.0
Liverpool
14 6
126.9
17 0
126.5
16 7
126.0
14 0
125.7
19 0
125.4
17 0
125.0
5 miles above Havana
21.0
124.0
15.7
123.0
122.4
Middle of "Hogfat Bend'' .......
16.3
10 8
121.0
120.0
Upper end "Havana Lake"
C. P. St. L. Piers, Havana
7.0
12.2
395
Connecting lake-acreage per mile of river-length between Copperas
Creek dam and Havana at the low gages of 1901 largely exceeded that
in any other section of river above or below, the figure of 472.1 acres
per mile being 57 per cent, more than between Chillicothe and the foot
of Peoria Lake and 23 per cent, more than between Havana and the
Lagrange dam — the two other reaches with the highest ratings. (Table,
p. 378.)
Though the eight or nine mile stretch of river just above Havana
has had more shore vegetation at recent summer levels than any other
section below Peoria Lake, the amount of vegetation bordering on chan-
nel of normal width (excluding such areas as Havana Lake) has not
in any recent season been very important. In a local fiat stretch of a
quarter mile on the west side above Liverpool, where there was more
shore vegetation both in 1913 and 191-1 than anywhere else between the
dam and the head of Havana Lake, the extreme width of the weed strip
was about 35 feet, a little less than 5% of the bank to bank width at
the time (about 750 feet) ; while for most of the distance it was not more
than 15 feet. Nowhere else between Copperas Creek dam and the head
of Havana Lake was there in 1913 or 1914 shore vegetation for any im-
portant distance that occupied more than a ten-foot strip next the bank,
and there were long stretches with much less than that amount. In the
shore zones of the wide water above the mouth of Spoon River there
are several acres of Potamogeton on the west side in the most favorable
seasons ; and on the east side a narrower strip, sometimes up to 50 or 60
feet wide, in a stretch of about 300 yards along the edge of Cook's
Island. Even these local areas, relatively to the vastly greater river
acreages wholly without aquatic vegetation in the 16.8 miles, are extremely
smiall, and revert largely to open water in all but the driest seasons.
Bottom Fauna. — A total of 16 channel collections and 23 collections
in the shore zones (within the 7-foot line) were made in July-October,
1915, between Copperas Creek dam and Havana in cross-section: at
Bottom Collections, Copperas Creek Dam to Havana
july-october, 1915
Channel
4— 7-ft.
zone
1— 3-ft.
zone
1. Copperas Creek dam to Mile 129
Mile 135.2, opposite head of Senate Island
Mile 133.6, opposite foot of Senate Island
4
4
2
2
2. Mile 129 to Havana
Mile 128.5, y2 mile above Liverpool
Mile 123.0, 3 miles above Havana
5
3
5
8
4
2
'Total
16
17
396
two stations in the shallower swifter section of 7.8 miles between the
dam and Mile 129 (1 mile above Liverpool) ; and at two stations in the
deeper more stagnant section of 9 miles between Mile 129 and Havana.
Although the entire section of over 16 miles is on the average
richer in small bottom animals than any other sections heretofore
treated, biologically, as well as in its hydrographical characters, it is sep-
arable into two well-distinguished portions, the half with the richer
channel bottom fauna being the deeper muddier section below Mile 129
and more immediately above the high Spoon-River bar. The average of
the poundages per acre at the channel stations in the lower half of the sec-
tion (5,156.0 lbs.) was in fact nearly six times the average valuation of
channel above Mile 129 (878.3 lbs. per acre), and almost fifteen times
the average valuation at the channel stations between Chillicothe and
the foot of Peoria Lake, Peoria Narrows excepted (345.1 lbs.).
Bottom Fauna, 1915, Copperas Creek Dam to Havana
pounds per acre (average total)
Channel
4 — 7-ft. zone
1 — 3-ft. zone
1. Copperas Creek dam to Mile 129
(7.8 miles)
878.3
1,436.2
No collections
2. Mile 129 to Havana (9 miles)
5,180.8
2,122.0
919.7
In the channel collections both above and below Liverpool the
larger Viviparidae made* up more than 99% of the weight of the average
collection. The Sphaeriidae and the smaller Gastropoda amounted in
weight to a mere trace in comparison; while the insects, worms, and
small Crustacea accounted for less than half of one per cent, of the
average poundages.
Bottom Fauna
Channel, Copperas Creek Dam to 1 Mile above
Liverpool, 1915
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Number per sq. yard,
Average
263.4
0.3
28.3
292.0
8 coll.'s
Pounds per acre,
Average
874.2
878.3
8 coll.'s
Per cent, of total,
(By weight)
99.5%
trace
0.4%
397
Bottom Fauna, Channel, 1 Mile above Liverpool to Havana, 1915
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Number per sq. yard,
Average
1,294.0
3.0
171.8
1,468.8
8 coll.'s
Pounds per acre,
Average
5,156.0
0.1
24.7
5,180.8
8 coll.'s
Per cent, of total,
(By weight)
99.5%
0.4%
Average bottom-fauna poundages in the, 4— 7-foot zone above Mile
129 in 1915 (1,436.2 lbs. per acre) were nearly twice those in the chan-
nel opposite (878.3 lbs.). Below Mile 129, where they were 2,122.0 lbs.
they were less than half the average channel valuation (5,180.8 lbs.).
No collections were taken above Mile 129 within the 4-foot line, but be-
tween Liverpool and Havana six collections in the 1-3-foot zone showed
an average valuation of 917.7 lbs. per acre. In the 4-7-foot zone, both
above and below Liverpool, Sphaeriidae were relatively much more
abundant than either in the channel or the 1-3-foot zone, making 40
to 80% of the average weight of collections. In the 1-3-foot zone below
Mile 129 the weight-composition of the bottom fauna was on the whole
nearly identical with that of the channel (Viviparidae and Pleuroceridae
96%; Sphaeriidae and smaller Gastropoda 2.3%; insects, etc., 1.1%).
Bottom Fauna, 4 — 7-foot Zone, Copperas Creek Dam to 1 Mile above
Liverpool, 1915
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Number per sq. yard,
Average
302.2"
1,212.5
96.0
1,610.4
4 coll.'s
Pounds per acre,
Average
814.3
606.2
15.7
1,436.2
4 coll.'s
Per cent, of total,
(By weight)
56.6%
42.2%
1.0%
398
Bottom Fauna, 4 — 7-ft. Zone, 1 Mile above Liverpool to Havana, 1915
.
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Number per sq. yard,
Average
120.8
3,537.3
172.0
3,830.1
13 coll.'s
Pounds per acre,
Average
319.3
1,776.7
28.0
2,122.0
13 coll.'s
Per cent, of total,
(By weight)
15.0%
83.7%
1.2%
Bottom Fauna, 1 — 3-ft. Zone, 1 Mile above Liverpool to Havana, 1915
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Number per sq. yard,
Average
Pounds per acre,
Average
Per cent, of total,
(By weight)
230.6
887.6
-96.5%
38.5
21.6
2.3%
81.0
10.5
1.1%
350.1
6 coll.'s
919.7
6 coll.'s
(e) Havana to Lagrange Dam (42.5 Miles)
Hydrography. — While the 42.5- miles of channel between Havana
and Lagrange has on the whole a swifter flow than the flatter reaches
above Havana, it is separable into three subdivisions which show dis-
tinct differences in slope and current :
1. The 17.2 miles between Havana and Sheldon's Grove (approxi-
mately Sharp's Landing), which has a low-water slope about the same
as Liverpool-Havana (0.53 inch per mile, low water, 1901), and a flood
velocity more than twice as great (140.91 feet per minute, March, 1903).
2. The 13.3 miles between Sheldon's Grove and one mile above
Beardstown, which had a low-water slope in 1901 (1.08 inches per mile)
about double that of the first 17 miles, but a flood velocity (116.06 feet
per minute, March, 1903) less than that of the first section.
399
3. The 12.0 miles between a point one mile above Beardstown and
the dam at Lagrange, where the slope of water surface in July, 1901, was
only 0.10 inch per mile, but the flood velocity (152.04 feet per second
in March, 1903) greater even than between Havana and Sheldon's
Grove.
Decline in Elevation of Low-Water Sueface, 1901; and Flood Velocity
Average slope
Flood velocity (av. ft.
Reach
Interval
inches
per minute, gage,
miles
per mile
18 ft., Peoria)
Havana to Sheldon's Grove 17.2
0.62
140.91 (17.2 miles)
Sheldon's Grove to 1 mile above
Beardstown
13.3
1.08
116.06 (14.3 miles)*
1 mile above Beardstown to La-
grange dam
12.0
0.10
152.04 (11.0 miles)*
The principal part of the first subdivision (the 13.8 miles between
Havana and the foot of Grand Island) as well as the lower 19.5 miles
of the reach (Browning to the dam), together making more than three
fourths of the entire reach of 42.5 miles, is comparatively wide and shal-
low, and has almost entirely sand or sand and shell bottom channel. The
muds found at the shore stations in 1915 were both lighter in color and
also less soft and deep than the soft shore deposits found above Havana.
At the low levels of 1901, depths in the channel between Havana and the
foot of Grand Island were as a rule 8 to 10 feet and ran at most a little
over 12; while below Browning they ranged usually between 10 and 12
feet and for short distances reached 13 to 15. Depths at recent midsum-
mer low levels have been 2 to 3 feet greater than these. Widths at the
low water of 1901 of single channel between Havana and the foot of
Grand Island were mostly 600 to 700 feet, and exceeded 750 feet for
short stretches ; and between Browning and the dam were usually over
700 feet and for good distances between 800 and 1,000.
The central section of about 9 miles of channel lying immediately
above the mouth of the Sangamon River (approximate foot of Grand
Island to 1 mile above Browning) is much narrower and deeper than
the stretches of channel above and below it, and. has a mud bottom.
Depths in this section of channel at the 1901 low levels were nearly
everywhere 15 to 20 feet; while bank to bank width was usually under
600 feet and fell for good distances under 500. The deep natural pool
lying above the Sangamon River bar is a homologue of those above the
great Farm Creek and Havana bars already described, and is of less mo-
ment biologically, in the respect of furnishing a very rich soil for bottom
animals, only because the entrance of this large tributary occurs in the
very midst of a 'long stretch of river with naturally steep gradient, where
* Nearest corresponding- velocity-reaches (Van Ornum float tests, March, 1903)
stop at Beardstown.
400
both increased velocities and increased flood volumes retard sedimen-
tation and keep the summit of the bar lower than in the other two cases.
Lake and other backwater acreage per mile between Havana and
the Lagrange dam (382.1- acres) exceeded at the low water of 1901 that
of any other reach of river except the 16.8 miles between Copperas
Creek dam and Havana.* The densest distribution of pond acreage oc-
curs in the 9 miles between the foot of Grand Island and the mouth of
the Sangamon and falls within the boundaries of greatest channel
depths, least flood velocity, softest and darkest-colored bottom deposits,
and richest bottom fauna, as shown by our collections of 1915.
Widths and Depths, Havana to Lagrange Dam
, Low Water, 1901
Miles
above
Grafton
Station
Width, ft.
Depth, ft.
max.
119.0
118.1
1 mile below Havana
658
768
549
640
530
732
712
457
514
658
475
582
439
494
878
750
732
658
1,006
1,000
514
841
732
732
805
933
8.5
8.7
10.7
10.0
12.5
8.3
9.0
9.1
7.0
11.0
14.7
12.4
18.4
15.6
20.4
17.0
13.4
8.7
8.3
10.2
13.2
12.8
10.2
13.1
12.1
8.5
10.5
11.7
15.0
11.8
11.7
1. Havana to foot of
Grand Island. Shal-
117.5
low section
116.0
115.0
114.0
113.5
111.9
Head of Grand Island
110.0
West channel only
108.0
106.5
106.2
104.0
1/3 mile above foot
of Grand Island....
Foot of Grand Island
2. Foot of Grand Island
to Browning. Nar-
102.8
101.6
row, deep section
98.0
98.2
Mouth of Sangamon..
97.0
95.7
93.0
1/4 mile below Brown-
iy2 miles below
3. Browning to Lagrange
dam. Wide, shallow
section
90.3
89.1
-
88.2
86.2
1/4 mile below wagon
bridge, Beardstown
84.2
83.6
82.6
81.5
80.4
78.8
78.6
77.7
250 yards above La-
* Table, p. 378.
401
Bottom Fauna. — A total of 58 bottom collections, at 9 stations, in
cross-section, were taken in 1915 between Havana and the Lagrange dam,
distributed between the channel and the shore zones and from north to
south as shown in the following table.
Collections, Havana to Lagrange Dam, 1915
Miles
above
Station
Channel
4 — 7— ft. zone
1 — 3-ft. zone
Grafton
1. Havana to foot Grand Island
(13.8 miles)
114.7
Opposite foot Matanzas Lake
500 yards above head of Grand
3
2
113.7
Island
3
2
8
2. Foot Grand Island to Brown-
ing (9.0 miles)
101.0
Opposite foot of Stewart Lake
1
4
2
97.0
1/4 mile below Browning
1
6
2
3. Browning to Lagrange dam
(19.7 miles)
89.5
1 mile above Beardstown
1
6
2
84.0
Brigg's Landing
2
83.2
Reich's Landing
2
80.3
Lagrange Landing
2
77.7
200 yards above dam
1
2
6
Total
16
22
20
With* reference to the bottom fauna this reach of 42.5 miles may
be described as a whole as a section of exceedingly poor channel, bor-
dered on either side by a comparatively rich shore fauna. The average
channel poundages of bottom animals taken in 1915 between Havana and
the dam at Lagrange was only 22 lbs. per acre, or not much more than
one fifteenth of average channel valuation between Chillicothe and the
foot of Peoria Lake (345 lbs.), and less than one two-hundredths of the
average between Liverpool and Havana (5,180 lbs.). While the channel
fauna was about equally poor throughout the 42.5 miles in 1915, the
shore fauna (bottom animals within the 7-foot line) was distinctly rich-
est in the central deeper section of river above the mouth of Sangamon
River, where the 4-7-foot zone showed figures (365.6 lbs. per acre) about
30% over the average of the 4^7-foot zone for the 42.5 miles, and
the 1-3-foot zone a rating (1,613.4 lbs. per acre) nearly four times the
42-mile average, or more in fact than was found anywhere else at that
depth between Chillicothe and Grafton. The greater part of the weight
of the average collections in the 42 miles, whether from channel or shore
zones, consisted of the larger snails (Viviparidae). Though larvae of
caddis-flies and nymphs of May-flies were relatively commoner than
above Havana, they were not numerous enough anywhere to contribute
402
importantly to weights, making up at the best only about 6 pounds of
the total acre valuation.
Bottom Fauna, 1915, Havana to Lagrange Dam
pounds per acre, average totals
Reach
Channel
4 — 7— ft. zone
1— 3-ft. zone
1. Havana to Lagrange dam (42.5 miles)
22.0
282.6
435.5
2. Foot of Grand Island to Browning
(9 miles)
12.5
365.6
1,613.4
Bottom Fauna, 1915, Channel, Havana to Lagrange Dam (42.5 miles)
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Number per sq. yard,
Average
5.5
6.0
3.7
15.2
16 coll.'s
Pounds per acre,
Average
16.0
3.0
3.0
22.0
16 coll.'s
Per cent, of total,
(By weight)
72.7%
13.6%
13.6%
Bottom Fauna, 1915, 4 — 7-foot Zone, Havana to Lagrange Dam (42.5 miles)
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Number per sq. yard,
Average
73.0
88.0
31.1
192.1
- 22 coll.'s
Pounds per acre,
Average
234.8
42.1
5.7
282.6
22 coll.'s
Per cent, of total,
(By weight)
83.0%
14.8%
2.0%
403
Bottom Fauna, 1915, 1 — 3-foot Zone, Havana to Lagrange Dam (42.5 miles)
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
"Total
Number per sq. yard,
Average
99.3
91.1
18.3
208.6
20 coll.'s
Pounds per acre,
Average
385.7
44.6
5.2
435.5
20 coll.'s
Per cent, of total,
(By weight)
88.5%
10.2%
1.1%
Bottom Fauna, 1915, Channel, Foot of Grand Island to Browning
(9 miles)
-
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Number per sq. yard,
Average
XI
2.5
1.0
6.2
2 coll.'s
Pounds per acre,
Average
1.5
5.0
6.0
12.5
2 coll.'s
Per cent, of total,
(By weight)
12.0%
40.0 %
48.0%
Bottom Fauna, 1915, 4 — 7-foot Zone, Foot of Grand Island to Browning
( 9 miles )
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Number per sq. yard,
Average
92.4 106.4
10.3
209.1
10 coll.'s
Pounds per acre,
Average
309.7
53.2
4.5
365.6
10 coll.'s
Per cent, of total,
(By weight)
84.2%,
14.5%,
1.2%
404
Bottom Fauna, 1915, 1 — 3-foot Zone, Foot of Grand Island to Browning
(9 miles)
•
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Number per sq. yard,
Average
327.4
186.2
26.1
539.7
4 coll.'s
Pounds per acre,
Average
1,516.0
93.1
4.3
1,613.4
4 coll.'s
Per cent, of total,
(By weight)
93.9%
5.7%
0.2%
(f) Lagrange Dam to Grafton (77.5 Miles)
Hydrography. — The average velocity in the 77.5 mile stretch of
channel between the Lagrange dam and the mouth of the river in March,
1903, at a gage of about 18 feet, Peoria, (172.30 feet per minute), was
more than three times that between Chillicothe and Peoria at the same
time (51.94 ft. per minute) ; more than twice that between Copperas
Creek dam and Havana (83.81 ft.)*; and exceeded that of any other sec-
tion of channel below. Chillicothe except the 9 miles between Peoria and
Pekin. The average decline in elevation of water surface at the 1901
low gages between Lagrange and the dam at Kampsville (0.85 inches per
mile) was more than three times the average through Peoria Lake; and
Decline in Elevation of Low-Water Surface, 1901; and Flood Velocity
Reach
Interval
miles
Av. slope
inches
per mile
Flood velocity (av.
feet per minute),
gage, 18 feet,
Peoria*
Lagrange dam (below) to Grafton
77.5
172.30
Lagrange dam (below) to Kampsville
dam (above)
46.1
0.85
164.24
Lagrange dam (below) to Florence
21.9
1.26
146.92
Florence to Kampsville dam (above)
24.2 0.49
183.85
Kampsville dam (below) to Grafton
31.4
2.44
186.91
* Van Ornum float tests, March, 1903.
405
in the 31 miles below Kampsville (2.44 inches per mile) was more than
in the short swift stretch between Peoria and Pekin.
A comparatively well-scoured channel bottom is found most of the
way from Lagrange to the mouth, sand, mud and shell, or dirty sand
prevailing, and such mud bottom as occurs being usually hard and
covered at most with only a very thin layer of recent silt. Inside the
7-foot line in 1915 a soft light-colored silt 2 inches to more than 12
inches deep was found at most of our collecting stations. The most im-
portant local stretches of muddy channel in 1915 were 6 miles imme-
diately above the Kampsville dam; and about 4 miles just above the
mouth of the river. A less important short section of muddy channel, in
Widths and Depths, Lagrange Dam to Grafton, Low Water, 1901
Miles
above
Grafton
Station
Width, ft.
Depth, ft.
max.
77.0
72.7
y2 mile below Lagrange dam
658
805
586
658
1,006
658
1,006
787
951
823
567
1,024
1,025
658
975
1,116
933
1,317
1,409
1,482
1,043
1,354
1,180
1,317
1,006
1,079
1,134
1,116
1,208
768
1,061
732
1,189
1,610
1,098
1,263
768
677
13.1
8.2
72.3
14.0
71.6
12.7
71.5
68.0
Meredosia
9.1
15.7
66.5
10.3
65.5 •
64.0
8.7
6.9
62.5
9.3
61.4
15.3
59.0
6.9
55.5
Florence
8.8
54.5
15.6
53.5
9.0
47.5
10.9
44.0
10.3
41.2
2 miles below Pearl
10.5
39.2
12.3
36.7
10.2
34.5
.
14.5
33.0
31.8
31.3
29.8
1 mile above Kampsville. . . .
500 yards above dam
300 yards below dam
11.3
13.7
10.0
20.0
25.8
9.2
21.3
20.3
8.1
6.5
16.9
7.2
12.3
14.7
11.5
8.1
10.0
19.2
8.5
7.8
7.3
6.5
Foot of Six Mile Island
8.7
14 0
5.5
14 2
4.0
14 4
3.0
18.4
406
the first mile below Six Mile Island — a local section with little drop in
levels at low water — had a deep deposit of light-colored mud in 1913,
but apparently much less two years later.
In the 46 miles between Lagrange and Kampsville extreme depths in
the channel at the low water of 1901 ranged from 9 to 11 feet as a rule,
and did not anywhere exceed 15 feet. Widths at these levels were be-
tween 1,000 and 1,400 feet for good stretches, and did not fall below 800
feet for any important distance. Below the Kampsville dam widths
were seldom' under 800 feet, ranging between 1,000 and 1,200 feet
for most of the way, and reaching a maximum of 1,600 in the sluggish
section just, below Six Mile Island.
Connecting lake and other backwater acreage per mile between La-
grange and the mouth of the Illinois at the low levels of 1901 (219.6
acres per mile between Lagrange and Florence; 180.0 between Florence
and' Kampsville; 86.9 between Kampsville and the mouth) compared
unfavorably with that of most of the river between Chillicothe and
Havana.* The greater part of this backwater was leveed and drained
between 1901 and 1913, resulting, no doubt, in recent years in a some-
what better scoured channel even than is indicated by the government
borings made between 1901 and 1905. As in the 42 miles above the
Lagrange dam, shore vegetation between Lagrange and the mouth of
the river has in recent years been a negligible quantity.
Bottom Collections, Lagrange to Grafton, 1915
Miles
above
Grafton
Station
Channel
4— 7-ft.
zone
1— 3-ft.
zone
71.7
60.0
55.6
54.5
47.7
43.2
36.5
33.0
31.6
Y2 mile above Mered'osia
iy2 miles below Valley -
Opposite Florence
1 mile below Florence
Total
% mile below Bedford
Opposite foot Pearl Island
%-way Apple Creek to Panther Cr.
1 mile above Kampsville
300 yards above Kampsville dam
4
2
1
6
1
5
1
6
1
1
25.7
20.6
11.5
9.3
8.5
7.3
Total. .
Opposite (west) head Diamond Is-
land
y2 mile below Hardin
1 mile below foot Mortland Island
Opposite Bloom's Landing
Opposite head Six-Mile Island
Below foot Six-Mile Island
5
17
1
1
2
1
4
2
1
4
1
2
Total
Grand total
7
16
12
31
12
28
* Table, p. 378.
407
Bottom Fauna. — In August, 1915, a total of 75 collections of the
bottom animals were made in cross-section at 15 stations between La-
grange dam and the mouth of the river, as shown in the preceding table.
The bottom-fauna valuations indicated between Lagrange and Graf-
ton by our collections of August, 1915, were almost uniformly poor both
in the shore zones and in the channel — the average of the sixteen channel
collections being only 6.7 lbs. per acre; that of 31 collections between
4— 7-feet, 16.7 lbs. ; and that of 28 collections within the 4-foot line, 16.9
lbs. The best local figures for the shore were obtained in the 4-7-foot zone
opposite Meredosia, where two hauls averaged 57.5 lbs. per acre ; and
in the 1-3-foot zone below Kampsville dam, where twelve collections
averaged 27.9 lbs. Both in the channel and in the shore zones, if we
except the 4-7-foot zone collections opposite Meredosia, Mollusca con-
tributed less or very little more to the average weight of collections than
did insects, worms, and small Crustacea, which together made up 63 to
65% of the average weight of collections in those depths zones, with
the noted exception. Of the latter group (non-Mollusca) the most im-
portant in weight were the larvae of caddis-flies in the channel, and the
immature stages of Ephemeridae (willow-flies) in the shore zones. As
these were principally of the new broods hatched from eggs deposited
by the adults which emerged only a month to six weeks earlier, they
contributed less to the weight of collections than they would have done
in the same numbers earlier in the summer or later in the fall. The
larger snails (Viviparidae and Pleuroceridae) amounted nowhere be-
low Lagrange to more than 5 or 10% of the weight of collections.
Bottom Fauna, 1915, Lagrange to Grafton
pounds per acre (average total)
Reach
Channel
4— 7-ft.
zone
1— 3-ft.
zone
1. Lagrange dam to Florence (21.9 miles)
/,*
57.5
2
10.1
8
2. Florence to Kampsville, above dam (24.2 miles)
12.4
5
16.6
7.5
8
3. Kampsville above dam to Grafton (31.4 miles)
6.5
7
10.3
2
27.9
12
Lagrange to Grafton (77.5 miles)
6.7
16
16.7
21
16.9
28
* The Italic figures give the number of collections.
408
Bottom Fauna, Channel, Lagrange to Grafton, 1915
pounds per acre
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Lagrange dam to Florence
4 coll.'s
....
....
....
trace
Florence to Kampsville
5 coll.'s
5.0
1.5
5.9
12.4
Kampsville to Grafton
7 coll.'s
2.6
3.9
6.5
Lagrange to Grafton
16 coll.'s
0.3
1.6
3.5
5.4
Per cent, of total
(by weight)
5.5%
29.6%
64.8%
Bottom Fauna, 4 — 7-foot Zone, Lagrange to Grafton, 1915
pounds per acre
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Lagrange dam to Florence
2 coll.'s
....
57.5
57.5
Florence to Kampsville
17 coll.'s
0.6
10.3
5.7
16.6
Kampsville to Grafton
12 coll.'s
....
4.8
5.5
■
10.3
Lagrange to Grafton
31 coll.'s
Trace
11.2
5.2
16.4
Per cent, of total
(by weight)
68.2%
31.8%
409
Bottom Fauna, 1 — 3-foot Zone, Lagrange to Grafton, 1915
pounds per acre
Viviparidae
and
Pleuroceridae
Small
Gastropoda
and
Sphaeriidae
Insects,
worms,
Crustacea
Total
Lagrange dam to Florence
8 coll.'s
....
9.2
0.9
10.1
Florence to Kampsville
8 coll.'s
2.4
0.1
5.0
7.5
Kampsville to Grafton
12 coll.'s
0.3
6.3
21.3
27.9
Lagrange to Grafton
28 coll.'s
0.8
5.3
10.8
16.9
Per cent, of total
(by weight)
4.7%
31.3%
63.9%
(g) General Summary, Illinois River Bottom Fauna,
July-October, 1915
1. distinction of main reaches
If we have regard only to the larger average differences in weight
of the bottom-fauna stocks of 1915, the 180.5 mile stretch of river be-
tween Chillicothe and Grafton separates into four principal subdivi-
sions : — First, a section of 43.7 miles between Chillicothe and the dam at
Copperas Creek which bears a fairly rich channel- and .a similarly rich
shore-fauna (channel average, 239 lbs. per acres ; 4 — 7-foot zone, 372 lbs. ;
1 — 3-foot zone, 225 lbs.). Second, a short stretch between Copperas Creek
dam and Havana which has an exceedingly rich channel fauna (3,029
lbs. per acre) and a shore fauna far above the average (4 — 7-foot zone,
1,960 lbs.; 1 — 3-foot zone, 920 lbs.). Third, 42.5 miles between Havana
and the dam at Lagrange with very poor channel (22 lbs. per acre) but
with shore as rich as in the first 60 miles (4 — 7-foot zone, 282 lbs. ;
1 — 3-foot-zone, 435 lbs.). Fourth, in the lower 77.5 miles, a long
reach that is extremely poor both in shore and channel (channel, 6 lbs.
per acre; both shore zones, 17 lbs.).
Whether in the shore or the channel zones, so far as is shown by
the data of 1915, the richest stocks of small bottom-invertebrates are
present in the reaches with the least flood slope and velocity, these
410
factors clearly influencing — more particularly, of course, in the channel —
both the depth and softness of the bottom deposits (regarded as a
medium or as a substratum for the bottom population), and also the food
supply of the bottom animals so far as it is brought to them by sedi-
mentation. In the two richer reaches of river above Havana the average
flood velocity in recent years (around 0.9 miles per hour) has been only
about Ys of that between Havana and Lagrange (1.5 miles per hour),
and less than half the average between Lagrange and Grafton (1.9
miles per hour).
Though there is usually, both in the slower and swifter reaches of
the river, if we except the cases of some sharp bends, some retardation
of current between mid-channel and shore, with accompanying increase
in sedimentation and noticeable differences in the composition of the bot-
tom populations, these differences in the less rapid sections above Havana
are neither very important quantitatively nor correlated so far as can be
seen. The average poundages per acre of bottom animals between Chilli-
cothe and Copperas Creek dam in the channel and the shore zones (chan-
nel, 239 lbs.; 4— 7-foot zone, 372 lbs.; 1— 3-foot zone, 225 lbs.) are in
fact so nearly the same that little if any significance can be attached to
the differences; while in the 16.8 miles between Copperas Creek and
Havana (channel, 3,029 lbs.; 4 — 7-foot zone, 1,960 lbs.; 1 — 3-foot zone,
920 lbs.) the differences in weight between the shore and channel stocks
are in the reverse of the direction that might be expected. There is,
however, a decidedly sharper contrast below Havana between the physical
characters of the channel and shore zones, and in and to either side of
the stretch of comparatively hard-bottomed channel between Havana and
Lagrange a corresponding contrast in the richness of the bottom fauna
that is without much question connected with it. In this section of 42.5
miles the 4 — 7-foot zone (282 lbs. per acre) had stocks thirteen times as
rich as those of the channel (22 lbs.) ; and there was a further large in-
crease shown in the stocks in the 1 — 3-foot zone.
Certain special influences that may affect the bottom-fauna yields
in the river below the Lagrange dam are discussed in a following sec-
tion.
2. ALL-ZONE AVERAGES AND TOTAL STOCKS
All-zone averages of the bottom-fauna stocks of the four main river
reaches below Chillicothe based upon rough acreage-weightings show a
figure for the first 43.7 miles below Chillicothe (264 lbs. per acre) about
the same as the average for the entire 180.5 miles between Chillicothe
and Grafton (261 lbs.) ; for the 16.8 miles between Copperas Creek dam
and Havana about ten times that (2,693 lbs.) : for the 42.5 miles be-
tween Havana and Lagrange a rate of yield (88 lbs. per acre) about
one third of the general river average and about one thirtieth of the rate
in the richest section; and for the 77.5 miles below Lagrange (10.4 lbs.
per acre) less than one twenty-fifth of the 180 mile average and less
411
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flood gage 18 ft.
Peoria
ft. per mm.
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412
than one two-hundredth of the rate between Copperas Creek dam and
Havana.
Figures for the total stocks present in the combined channel and
shore acreage below Chillicothe July-October 1915 (table, p. 18), based
on these all-zone weight valuations and on approximate acreages for
average July-October levels in 1910 — 1914, show that out of total stocks
equaling 6,988,103 pounds for about 26,700 acres, 92.7 per cent., or
6,480,952 pounds, were in the 60.5 mile section of river above Havana —
this constituting only one third of the total length of river studied and
less than one third of the total river acreage. Again, of the total bottom-
fauna stocks 53.9%, or 3,770,200 pounds, were in the 16.8 miles of river
between Copperas Creek and Havana — which comprises less than one
tenth of the total distance between Chillicothe and the mouth, and only
about one twentieth of the total acreage. The stocks between Havana
and Lagrange, 396,880 lbs., for 42.5 miles, made up but 5.6% of the
grand total ; and those between Lagrange and Grafton, 110,271 lbs.,
for 77.5 miles, only 1.5 per cent.
Bottom Fauna, Illinois River, 1915. Acreage-weighted All-Zone Averages
pounds per acre
Reach
Miles
Approx. acres
Gage, 8 ft.
Havana
Estimated
part of
total under
7 ft. deep
Bottom
fauna
lbs. per acre
(average)
Chillicothe to Copperas Creek
dam
43.7
10,268*
1/3
264
80f
Copperas Creek dam to Havana
16.8
1,400
1/4
2,693
39
Havana to Lagrange 42.5
4,510
1/5
88
58
Lagrange to Grafton
77.5
10,603
2/5 10.4
15
Chillicothe to Grafton
180.5
26,782
261
252
Average Chillicothe to Copperas Creek dam, 555 lbs.
Average Copperas Creek dam to Lagrange, 705 lbs.
3. COMPOSITION OF THE BOTTOM FAUNA
In the section of river above Lagrange dam, both in the channel and
in the shore zones, the great bulk of the bottom-fauna poundages was
made up of Mollusca (Gastropoda and Sphaeriidae), the percentages by
* Includes Peoria Lake.
t The Italic figures give the number of collections.
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weight running in these reaches from 86 to over 99%, and falling below
90% only in the 1 — 3-foot zone above the Copperas Creek dam. Below
the Lagrange dam, where the large Ephemeridae (May-flies) were rela-
tively much more abundant than farther north, the Mollusca percentages
dropper to an average range between 35 and 68%.
In the sections above Lagrange, if we except the 4 — 7-foot zone
between Copperas Creek dam and Havana, the larger snails (Viviparidae
and Pleuroceridae) accounted for 70 to nearly 100% of the Mollusca
totals (by weight). Below Lagrange the Viviparidae (and Pleuroceri-
dae) were largely replaced by Sphaeriidae in all zones, the weight per-
centages of that group rising to a range between 84 and 100%.
Bottom Fauna, Illinois River, 1915
Percentages of Average Total Valuations by Weight .
contributed by mollusca
Channel
4— 7-ft.
zone
1— 3-ft.
zone
Chillicothe to Copperas Creek dam
96.7
97.3
92.1
Copperas Creek dam to Havana
99.5
98.8
98.8
Havana to Lagrange
86.3
98.1
98.9
Lagrange to Grafton
31.6
65.8
35.8
Bottom Fauna, Illinois River, 1915
Composition of Mollusca Totals. (Percentages by Weight*)
Viviparidae and
Pleuroceridae
Sphaeriidae and small
Gastropoda
Reach
Channel
4— 7-ft.
zone
1— 3-ft.
zone
Channel
4— 7-ft.
zone
1— 3-ft.
zone
Chillicothe to Copperas
Creek dam
78.5
78.1
70.7
21.5
21.9
29.3
Copperas Creek dam
to Havana
100.0
22.5
97.7
trace
77.5
2.3
Havana to Lagrange
84.3 84.8
89.7
15.7
15.2
10.3
Lagrange to Grafton
15.8
none
13.2
84.2
100.0
86.8
* Pound values on which these percentages are based are shown in following
tables.
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418
The Bottom Fauna of the Lakes and Ponds of the Illinois River
Bottom-lands between Copperas Creek Dam and
Lagrange, July — October, 1914 — 1915
1. Hydrography and Physical Features
In the midsummer and autumn months of 1914 and 1915 a total
of 266 bottom collections, principally with the mud-dipper, were made in
the lakes and ponds and other backwaters in the river bottoms between
the head of Clear Lake and the foot of Sangamon Bay, covering a river
distance of 39 miles, and representing an ex-river acreage (about 16,000
acres) at a gage of 8 feet, Havana, around one third of the total prevailing
at the time between the Copperas Creek and Lagrange dams (about 52,000
acres).
The lakes and backwaters studied, separate naturally on a basis of
physical and hydrographical features into five classes :
I. The deeper lakes of the all-bottom-land type, with flat muddy
banks on both sides, and with maximum depths at recent midsummer
levels between 7^ and 9 feet. The five lakes of this class examined —
Clear — Mud, Liverpool, Thompson, Dogfish, and Sangamon Bay — have
deep soft black mud bottom in the central deeper portions, and only
rarely a little sand near shore. The vegetation, principally Potamogeton
and Ceratophyllum, is confined to the rather wide shallow margins, the
most of it well within the zone of 0 — 6 feet. These lakes ranged in size
at the low water of 1901 (4.2 ft., Havana) from 275 to about 1,800 acres,
and represented in all at that gage about 3,390 acres. At the average
gage of July — October, 1910 — 1914 (approximately 8 ft., Havana), their
acreage is somewhere near %y2 times the 1901 figures, or over 8,000
acres, which is close to one seventh of the total lake acreage between
Copperas Creek dam and Lagrange, and more than the total river acreage
at the same gage in the same distance (about 6,000 acres).
II. The deeper, sand-beach type, bordering on one side against the
sandy bluff, and with sandy shore on that side, but with flat muddy banks
opposite. The two lakes of this type studied (Quiver and Matanzas)
had a total acreage at the low water of 1901 of more than 600 acres), and
maximum depths at recent midsummer levels of 8J^ to 12 feet. In
Quiver Lake there is some sand and large quantities of old shells mixed
with the mud in the deep "channel" which is kept open by the water from
Quiver Creek during freshets. In Matanzas Lake the central open por-
tion has all a soft black mud bottom. The vegetation in these two lakes
is in its character and in its distribution not essentially different from
that of the lakes of Class I, though it is inclined to be rather less dense
on the average. These lakes receive a comparatively large amount of
spring water from the sandy bluff on the east side, and their waters
average somewhat clearer and (except at times of invasion by river
water) poorer in plankton than the lakes of the all-bottom-land type.
419
III. The comparatively shallow, weedy lakes, with maximum
depths at gage 8 feet, Havana, of about 5 feet. The lakes of this class
in which collections were made in 1914 and 1915 (Flag, Seebs, Stewart)
represented a total acreage at the low water of 1901 of about 1,500 acres,
and at 8 feet, Havana, somewhere near 4,000. All of these lakes went
completely dry in seasons of extreme low water before 1900. Both in
the shallower and the deeper portions the black bottom deposits con-
tain a much larger percentage of partially decayed dead vegetation than
is found in the open waters of the lakes of Class I. In recent midsummer
seasons, up to 1914, Flag and Seebs lakes have been almost completely
filled with growing vegetation. In Stewart Lake at the same time some
open water was to be found in the central deeper portion toward the
foot, but much less relatively to the total area than was the case in such
lakes as Thompson and other deeper lakes of its type.
IV. The very shallow, very weedy lakes, with greatest depths at
the low water of 1910 — 1914 between o1/^ and 4 feet. These lakes
(Duck, Dennis, Crane) were little more than lily or flag ponds before
1900, going wholly dry at low water in most seasons before the opening
of the Chicago Sanitary Canal. Between August and October, 1914,
Duck and Dennis lakes were so filled with mixed vegetation that it was
difficult to pass through them with a skiff, even the fallen dead stems
of the coarse water-plants being blanketed with living filamentous
algae. Crane Lake in 1914 and other recent years has been a vast lily-
bed, with its rather more open, but densely shaded bottom sprinkled
with dead lily stems and "yorkey-nuts". These three lakes had a low-
water acreage in 1901 around 1,200 acres.
V. The shallow dead timber and brush areas first permanently
submerged after the opening of the Sanitary Canal in January, 1900.
These shallow backwaters, ranging in depth from 1}4 to 4 feet over
most of their areas, have alternating opener and densely weeded
stretches, the prevailing vegetation being Potamogetom and Polygonum.
Their location on the ridges between such lakes as Flag and Thompson,
and on similar ridges between these lakes and others and the river,
makes them in reality littoral, either of the river or of lakes of the pre-
ceding classes, as the case may be. Their bottom soil still contains
abundant traces of the sticks and dead leaves contributed by the willows
and mallows and button-bushes that grew there 20 years ago. The area
represented by waters of this type can only, for the present, be roughly
estimated. The total area under 4 feet in depth at the July-October levels
of recent years between Copperas Creek and Lagrange dams (about 29,700
acres) made up over 50% of the total ex-river acreage, while careful
estimates in the case of Thompson Lake as flooded to the same elevation
(approx. Havana 8 ft.) indicated that on that gage in this lake these areas
made up about 30% of the total land flooded. The dead timber and brush
areas studied by us in 1914 and 1915 were all in the vicinity of Havana
and were variously contiguous with Clear, Flag, Thompson, Dogfish,
and Quiver lakes.
420
2. Bottom Fauna of the Lakes, by Classes
Class I. — Fifty-three collections from open water over 6 feet in
depth in the deeper all-bottom-land lakes of Class I in 1914 and 1915
averaged 222 pounds per acre of bottom animals, after deducting shells
of Mollusca. An average about twice as great (441 lbs.) was shown by
78 collections from the 1 — 6-foot zone, 21 of these hauls coming from
open bottom and having an average of 696 lbs. per acre, and 57 from
more or less weedy bottom, with an average of 347 lbs. The average
of the total of 131 collections from the five lakes, all depths, in both
seasons, was 352 pounds. Forty-two of the total 131 collections were
taken in 1914 and 89 in 1915.
Thompson Lake, both in 1914 and 1915, easily outranked the other
lakes of its class studied in the richness of its bottom fauna, its average
of over 540 lbs. per acre, in either season, being more than double the
best other lake average in this class, (Dogfish,) and nearly three times
the lowest (Liverpool).
Class II. — The two sand-beach lakes (Quiver and Matanzas)
showed a combined average for 1914 and 1915, for open water over 6
feet, of 1,667 lbs. per acre, for a total of 27 collections. Of these, 18
were from Quiver Lake, with an average of 2,471 lbs., and 9 from
Matanzas Lake, with an average of only 58 lbs. per acre. The combined
average of 37 collections, from the 1 — 6-foot vegetation zone, was 251 lbs.,
the average of Matanzas again being lower than that of Quiver. The
general average, for the total of 64 collections, both lakes, both years,
and all depths, was 848 lbs. per acre, or more than twice that of the
lakes of Class I. It will be noted, however, that the very high average
for this class and for Quiver alone, was largely due to a few enormous
hauls of large Viviparidae in the deep "channel" in 1914. These were
much reduced in numbers and weight per acre in 1915.
Classes III, IV, V. — The shallow weedy lakes of Class III, Flag,
Seebs, and Stewart, averaged only 57 lbs. per acre, combined average of
45 collections, all depths, both seasons ; and the very shallow, very weedy
lakes (Duck — Dennis, Crane) only 94 lbs. per acre for a total of 10
collections. As will be shown in the next section, however, it was in
these shallower, weedier lakes, and in other weedy backwaters, that the
shore animals in the weeds (above the bottom) reach their highest
figures. In the dead timber and brush areas the bottom-fauna average
of 16 collections, 1914 — 1915 (187 lbs.) was better than in weedy lakes
of Classes III and IV, approaching, in fact, the average of the open
water of the deep lakes of the all-bottom-land type (222 lbs.).
421
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425
3. General Average Valuation
A simple average (without weighting to compensate for irregularity
in distribution of collections within different lake classes) of the total
of 266 bottom collections of 1914 — 1915 from the five classes of lakes
and backwaters (including dead timber and brush areas) figures out
at 402 lbs. per acre. Since the general average of 848 lbs. per acre for
the Class II lakes (Quiver, etc.) applied to but 620 acres at the low
water of 1901, while the average of 352 lbs. per acre for the Class I
lakes covered 3,390 acres at the same gage, it is evident that a simple
average of this sort is unfair and likely to be unduly high. As we have
not complete acreage figures for different depths at recent gages pre-
vailing in midsummer, and lack, in particular, exact figures on the dead
timber acreage, a close general average of all the lakes and backwaters
studied in the two years, based on accurate acreage weightings, can not
now be figured. If we assume, however, that on the average the ex-
pansion in lake acreage between 4.2 and 8 feet, Havana, is about the
same in all of the first four classes of lakes except Class II, we shall
not go far wrong in weighting the class average of I to IV, excluding
the dead timber and brush areas, with the low-water acreage for 1901.
The general bottom-fauna average for Classes I — IV, inclusive, figures
out in this way at 285 lbs. per acre. If, again, we assume that the usual
ratio of adjacent dead-timber acreage to the total acreage of lakes and
backwaters at gage 8 feet, Havana, is about the same as in Thompson
Lake (around 30%, estimated), and weight the Class I — IV average
(285 lbs.) and the Class V average (187 lbs., dead timber and brush
areas) with "per cent." acreage figures on this basis, we obtain a gen-
eral average of bottom fauna for the two years, for all classes of lakes
and backwaters, all depths, of 255 lbs. per acre, or almost exactly the
general river average for 180.5 miles below Chillicothe (261 lbs.), but
only about one third of the all-zone river average for the 59.3 miles be-
tween Copperas Creek and Lagrange dams (705 lbs.).
426
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4. Composition of the Bottom Fauna
The proportion of Mollusca to associated animals in the lake col-
lections of 1914 — 1915 did not run so uniformly high as in the river
series of 1915. The Mollusca percentages are highest in the open water
of the deeper lakes of Classes I and II, where they run from 84 to 96%.
In the weedy zones (1 — 6 feet) of the deeper lakes the Mollusca per-
centages were noticeably lower (77%). In the shallower weedy lakes
of Classes III and IV the insects and small Crustacea are much more
abundant relatively, and the Mollusca ratios drop to 36 and 50%.
Per Cent. Mollusca by Weight (to Total Weight of Collections),
Lakes, 1914—1915
Zone over
6 feet
1—6 ft.,
1—6 ft.,
open water
no vegetation
vegetation
Class I
84.1
89.8
77.8
Class II
96.8
• . . *
77.5
Class III
• • • •
• » . .
50.7
Class IV
• • • «
36.4
Class V
....
79.7
The snail fauna of the lakes, like the insect fauna, presents in the
average somewhat greater variety than that of the river. Viviparidae
made up1 the largest percentage of the Mollusca totals in the deeper lakes
of Classes I and II. In the shallower weedy lakes and in the dead timber
areas the ratios of Viviparidae were lower. The smaller snail fauna
(smaller Gastropoda, Sphaeriidae) less rarely than in the river consisted
almost exclusively of Sphaeriidae' — the Valvatidae and Amnicolidae
being well represented in most of the lakes studied, and exceeding
Sphaeriidae in some cases, in the shallower weedier lakes, both in num-
bers and weight.
Further details of the composition of the lake bottom-fauna are
shown in the detail tables at the end.
Pee Cent, of Viviparidae, by Weight, to Total Weight of all Mollusca,
Lakes, 1914—1915
Zone over
6 ft.
open water
1—6 ft.,
no vegetation
1—6 ft.,
vegetation
Class I
Class II
Class III
Class IV
Class V
56%
99%
85%
86%
88%
62%
61%
77%
428
Illinois Valley Lakes, 1914 — 1915, Bottom Fauna
pounds per acre
I. Deep Bottom-land Type. (Zone over 6 feet)
Lake
No. col-
lections
Large
Viviparidae
etc.
Sphaeriidae
etc.
Insects
etc.
Total
Per cent.
Mollusca
Clear— Mud, 1915
8
17.1
186.8
11.7
215.6
94
Liverpool, 1915
6
24.3
96.7
21.2
142.2
85
Thompson, 1914
8
76.5
140.0
94.2
310.7
69
Thompson, 1915,
8
413^9
64.6
18.1
496.6
96
Dogfish, 1914
3
8.0 3.1
12.3
23.4
47
Dogfish, 1915
12
67.1 18.5 66.4
152.0
56
Sangamon, 1915
10
51.2
41.4
14.0
106.6
86
Average
53
104.6
82.2
35.2
222
84.1%
Illinois Valley Lakes, 1914 — 1915, Bottom Fauna
pounds per acre
1. Deep Bottom-land Type. (1 — 6-ft. Zone. No Vegetation)
Lake
No. col-
lections
Large
Viviparidae
etc.
Sphaeriidae
etc.
Insects
etc.
Total
Per cent.
Mollusca
Thompson, 1914
10
687.1
80.3 :
135.8
903.2
85
Thompson, 1915
*
7
610.5
24.9
12.2
647.6 98
Sangamon, 1915
4
145.3
109.5
10.2
265.0
96
Average
21
558.3
67.3
70.6
696
89.8%
429
I. Deep Bottom-land Type. (1— 6-ft. Zone.
Vegetation)
Clear— Mud, 1915
12
121.7
110.7
17.7
250.1
93
Liverpool, 1915
9
117.0
4.2
28.2
149.4
85
Thompson, 1914
16
210.0
28.4
193.1
431.5
55
Thompson, 1915
12
481.9
10.0
20.4
512.4
95
Dogfish, 1914
5
336.0
19.1
42.4
397.5
89
Dogfish, 1915
3
none
7.3
-
126.9
134.2
5
Average
57
233.9
36.1
77.0
347
77.8%
Illinois Valley Lakes, 1914 — 1915, Bottom Fauna
pounds pee acre
II. Deep, Sand-Beach Type. (Zone over 6 feet)
Lake
No. col-
lections
Large
Viviparidae
etc.
Sphaeriidae
etc.
Insects
etc.
Total
Per cent.
Mollusca
Quiver, 1914
15
2,754.6
2.9
47.5
2,805.0
98
Quiver, 1915
3
800.0
none
3.1
803.1
99
Matanzas, 1915
9
i
none 40.6
18.0
58.6
69
Average
.27
1,619.2
15.1
32.7
1,667
96.8%
II. Deep, Sand-Beach Type.
(1— 6-ft. Zone
Vegetation)
Quiver, 1914
17
329.7
33.4
25.2
388.3
93
Quiver, 1915
14
35.5
9.3
113.9
158.7
28
Matanzas, 1915
6
• 58.4
9.6
9.9
77.9
87
Average
37
174.3
20.4
56.2
251
77.5%
430
Illinois Valley Lakes, 1914 — 1915, Bottom Fauna
pounds per acre
III. Shallow, Weedy Type. (Depth 1—5 ft.)
T , No. col-
lections
Large
Viviparidae
etc.
Sphaeriidae
etc.
Insects
etc.
Total
Per cent.
Mollusca
Flag, 1914 3
none
25.7
45.2
70.9
63
Flag, 1915
15
5.0
none
22.9
27.9
18
Seebs, 1914
7
14.0
15.5
94.5
i
124.0 j 24
Seebs, 1915
8
18.5
1.8
5.6
25.9
78
Stewart, 1915
12
41.0
24.4 8.4 73.8
| 1
88
Average
45
18.0
10.9
28.1
57
50.7%
Illinois Valley Lakes, 1914 — 1915, Bottom Fauna
pounds per acre
IV. Very Shallow, very Weedy Type. (Depth 1 — 4 ft.)
Lake
Large
No. col- Viviparidae
lections | etc.
Sphaeriidae
etc.
Insects
etc.
Total
Per cent.
Mollusca
Duck — Dennis, 1914
5
none
12.4
97.9
110.3
11
Crane, 1915
5
42.0
14.3
22.7
79.0
71
Average
10
21.0
13.3
60.3
94
36.4%
V. Dead Timber and Brush Areas. (Depth 1 — 4 ft. Vegetation)
Vicinity Havana, 1914
6
29.8
87.1
44.0
160.9
72
Vicinity Havana, 1915
10
167.5
1.3
33.6
202.4
83
Average
16
115.8
33.4
37.5
187
79.7%
431
The Weed-Fauna of the 1— 4-foot Zone of the Illinois Valley
Lakes, and the Combined Bottom- and Weed-Fauna
Average, August— -October , 1914
1. Weed Fauna of the Lakes near Havana
In the autumn of 1914 a series of quantitative collections of the
small invertebrates attached to and scattered between the leaves and
stems of the denser growths of coarse vegetation about the margins of
the bottom-land lakes near Havana, in depths 1 to 4,y2 feet, were made
at seven stations. These collections were made by inclosing the tops of
the plants .in a large bucket, lowered about them to a depth of about 9
inches, cutting off the stems a little below the 9-inch level, shaking them
out thoroughly in the water obtained by righting the bucket, and then
passing the water saved through a fine sieve. Though these collections
represent but a fraction of the total "weed fauna", omitting the small
insects and other animals occurring between the bottom and the lower
limit of the bucket hauls (a distance of 1 to 3 feet), the average valua-
tions obtained in this way were very much above the average bottom
valuations from the same lakes in any zone, with the single exception
of a few hauls from the bottom of the Quiver Lake "channel" in 1914.
The general average for the seven stations was in fact 2,118 lbs. per
acre, or more than eight times the general average of bottom fauna for
the five classes of lakes and backwaters between the head of Clear Lake
and Beardstown studied by us in 1914 and 1915 (255 lbs.).
The smaller snails (Amnicolidae, Physidae, and Valvatidae, prin-
cipally) formed about 50% of the average total by weight. The ap-
proximate half of the collections made up of insects (larvae and nymphs)
consisted principally of immature Odonata (Agrionidae and small Libel-
lulidae). The only large snails were a few adult Planorbis trivolvis,
the great bulk of the material being of quite small size and easily avail-
able, in that respect, for use as food by young to half-grown as well as
adult fishes.
2. Combined Average Valuation of the Bottom- and Weed-Fauna
Stocks, and Total Stocks in the Acreage
For the purpose of calculating a general average, and also the total
stocks, both of the bottom and weed animals, for the entire lake and
other backwater acreage between Copperas Creek dam and Lagrange
(approximately 52,700 acres at 8 feet, Havana — the average gage in
July — October, 1910 — 1914), I have assigned the general bottom-fauna
average of the twelve lakes studied (255 lbs.) to the entire acreage, as
with no levees, and the weed-fauna average of the lakes in the imme-
diate neighborhood of Havana (2,118 lbs.) to the approximate 29,700
acres with depths under 4 feet in the district. An acreage-weighted
general average figured in this way stands at 1,447 lbs. per acre, or at
432
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more than twice the all-zone river average for bottom fauna only in the
same distance (705 lbs.), and at more than 5^ times the average
figures for bottom fauna only in the lakes and other backwaters be-
tween the two dams in 1914 and 1915 (255 lbs.).
The total stocks in the entire 52,760 acres of lakes and ponds
(acreage as with no levees, substantially same as 1908 rather than
1914 — 1915, for purpose of comparison with fish yields of that year),
76,358,400 lbs. is more than 10 times the total stocks in the 59.3 miles
of river opposite (6,988,103 lbs. for 26,700 acres). Of the total, 13,-
453,800 lbs., or 17.6%, represents the bottom animals of the full acreage;
and 62,904,600 lbs., or 82.3%, represents the small weed animals of the
upper 9 inches only, in the rather more than 50% of the total acreage
within the 4-foot line.
Bottom- and Weed-Fauna Stocks, Lakes, Coppeeas Creek Dam to
Lagrange (59.3 miles)
Approx. acreage
8 ft., Havana
(No levees)
Average valuation*
pounds per acre
1914—1915
Total stocks
for acreage in
first columnf
Per cent.
of
total
Bottom fauna
stocks — all
depths
52,760 a.
255
13,453,800
17.6%
Weed fauna
stocks — 1 — 4
ft.
29,700 a.
2,118
62,904,600
82.3%
Bottom and
weed stocks
52,760 a.
1,447
76,358,400
The Bottom- and Weed- Fauna of the Littoral Zone of the Deep
Glacial Lakes of Northeastern Illinois,
August — October, 1916
1. Bottom Fauna
The general average of 119 mud-dipper collections from the zone
of 1 — 7 feet in eight of the deep glacial lakes of northeastern Illinois
in August — October, 1916, was only 82.8 lbs. per acre. The six isolated
lakes studied (Deep, Cedar, Zurich, Crystal, Long, and Sand lakes)
showed the better average (105.8 lbs.), while the two large lakes (Fox
and Pistakee) directly open to the channel of Fox River averaged only
54.2 lbs. Sparse vegetation, principally species of Potamogeton, with
some Chara, chiefly within the 3-foot line, were present at most of the col-
lecting stations. The bottom varied from sand, gravel or sandy mud, to
soft black mud or yellow clay. On the windward side (southeast or west)
of most of these lakes there is a more or less sterile clay zone with very
* Based on data from 12 lakes representing around half of the total acreage,
t Equals approximately that of 1908. (Table originally made for comparison
with 1908 fish yields.)
434
scanty vegetation, or none at all, lying between the weedy shore zone
and the deep open water, part of it sometimes extending within the 7-
foot line.
Valuations considerably better than the average were obtained in
restricted areas with more nearly uniform bottom in four of the isolated
lakes, the average for clay bottom overlaid with fine decayed vegetation,
in Deep Lake being 320 lbs.; for sand and clay, in Cedar Lake, 251 lbs.;
for gravel and sand, in Deep Lake, 220 lbs. ; and for gravel and sand,
in Lake Zurich, 212 lbs.
In its composition the littoral bottom-fauna of these lakes differs
most strikingly from that of the Illinois Valley bottom-land lakes in the
relatively much lower percentages of Mollusca. Snails made up only
Lakes, Northeastern Illinois, August — October, 1916, Bottom Fauna
pounds per acre
Littoral Zone, 1 — 7 feet. Some Vegetation
Lake
Number
of col-
lections
Large
Viviparidae
etc.
Sphaeriidae
etc.
Insects
etc.
Total
Per cent.
Mollusca
Deep
Cedar
24
169.0
208.8
24.2
135.6
159.8 v
19
15
Zurich
13
9.9
10.0
49.2
69.1
23
Crystal
6
16.0
40.4
56.4
28
Long
6
1.7
50.7
52.4
3
Sand
10
0.6
13.1
13.7
4
Average
66
1.8
16.7
$7.1
105.8
17.4%
Pistakee
29
10.8
26.0
42.6
79.4
46
Fox
24
2.3
3.6
18.0
23.9
24
3m
435
17.4% of the average weight of the hauls at 66 stations in the six iso-
lated lakes; and only 41.8% in the two lakes traversed by the Fox River
channel. The snails belonged almost entirely to the smaller-sized
species, the larger Pleuroceridae ' and Viviparidae occurring only very
rarely and in small numbers in the hauls. The most abundant families
were the Sphaeriidae, Amnicolidae, Valvatidae, and Physidae. The most
important insects, measured by weight, were the Trichoptera (caddis-
flies), Chironomidae, and large Ephemeridae (May-flies).
(A more complete report on these collections, including also the
dredgings in deep water, is being planned for publication later.)
2. Weed Fauna
In August, 1916, we found the shore vegetation of the isolated glacial
lakes so generally thin and sparse, as compared with the dense growths
of Potamogeton and Ceratophyllum in the Illinois River bottom-land
lakes, that it was practically impossible to employ the bucket method of
collecting the weed animals used at Havana in 1914. Along the north
shores of Pistakee and Nippersink lakes, however, beds of mixed
Potamogeton, Myriophyllum, and Ceratophyllum were not uncommon
that were fully as dense and that carried not far from as rich a fauna
as that of such lakes as Flag and Thompson. The average for the upper
9 inches at two stations in Pistakee and Nippersink lakes in August, 1916
(1,665 'lbs. per acre), was only 26% less than the average of the seven
weed-fauna stations in the vicinity of Havana in 1914 (2,118 lbs.). Both
insects and mollusks constituted an almost insignificant part of the
totals, 85% of the weight in one case, and 95% in the other being made
up of a single small crustacean — the little fresh-water shrimp, Hyalella
knickerbockeri. (Table, p. 436.)
Comparison with Outside Bottom- and
Weed-Fauna Valuations
1. Bottom- and Weed- Faun a of Oneida Lake. (Baker, 1918)
In the Lower South Bay of Oneida Lake, New York, in 1916, Baker
found the richest bottom-fauna within the 6-foot contour. Averaged
by weight*, in pounds per acre, sand bottom showed the highest valua-
tions, 143 sixteen square-inch units examined, averaging 387 lbs. Gravel
bottom, with 207 lbs., clay bottom, with 188 lbs., and sand and clay,
with 210 lbs., were well under sand bottom in richness, but were all much
436
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exceed the average figures obtained by us in 1916 in the same depth
zone in the isolated glacial lakes of northern Illinois (105 lbs.), but do
not average much if any better than the best littoral areas in Deep and
Cedar lakes (Deep Lake, gravel bottom, 220 lbs., clay and rotten vegeta-
tion, 320 lbs.; Cedar Lake, sand and clay bottom, 251 lbs.). They com-
pare very well with the all-depth average (one to eleven feet) for the
Illinois Valley lakes of all classes in 1914 and 1915 (255 lbs. per acre),
but are exceeded by the general average of bottom fauna only in the 1 — 6-
foot zone of our Class I lakes in the Havana district (441 lbs.) ; and are
far surpassed by the figures for the 1 — 3- and 4 — 7-foot zones of the
Illinois River between Copperas Creek dam and Havana (1 — 3-foot
zone, 919 lbs.; 4 — 7-foot zone, 1,960 lbs.). The ratio of Mollusca to the
total weight of all animals averaged much higher (38% to 64%) than
in the glacial lakes of northern Illinois, but was far under the ratios
found in the Illinois River and in the lakes near Havana.
Bottom Fauna of Oneida Lake, 1 — 6-foot Zone
pounds pek acee (our valuations)
Mollusca
Associated
animals
Total
Per cent.
Mollusca
Sand bottom
251.3
138.3
389
64
Mud bottom
96.9
133.5
230
42
Sandy clay
81.4
129.3
210
38
Gravel
139.4
68.2
207
67
Clay
75.3
112.7
188
40
While Baker found in Oneida Lake, in a few situations, a weed fauna
(total, picked by hand from plants removed from the water) that ap-
proached in valuation his bottom-fauna averages for the littoral zones,
the average productivity indicated ran very low, and even his heaviest
collections (57 to 207 lbs. per acre, our valuations) were far below
those obtained by us in the lakes of the Illinois Valley near Havana
(2,118 lbs. average) or in the thick Potamogeton and Ceratophyllum beds
of Nippersink and Pistakee lakes (1,655 lbs.). Baker's best figures were
obtained in the Potamogeton and Myriophyllum, and the bulk of the
collections by weight was made up of snails.
438
2. Bottom Fauna of Lake Mendota. (Muttkowski, 1918)
Average valuations in pounds per acre for the 0 — 1- and 1 — 3-meter
zones obtained by Muttkowski in Lake Mendota in 1914 and 1915 (60
and 64 lbs. respectively) are slightly higher than our averages of 1916
from the 1— 6-foot zone of Fox and Pistakee lakes (54 lbs.), but are
well under the average for the six isolated glacial lakes (105 lbs.).
Mollusca formed only 4% of the total average weight in the 0 — 1-meter
areas, and 14% in the 1 — 3-meter zone. The most important groups of
animals as measured by weight were the larvae of Chironomidae and
Trichoptera.
Bottom fauna of Lake Mendota, Wisconsin. 1-
poitnds pee acre (que valuations)
-3 METERS
Mollusca
Others
Total
Per cent.
Mollusca
0 — 1 meter
2.59
57.37
60
4
1 — 3 meters
9.40
55.12
64
14
Marine Bottom-Fauna Valuations,
(Petersen, 1911—1918)
Denmark
The marine bottom-fauna valuations, by rough weight, obtained by
Petersen 1910 to 1916 included the shells of Mollusca and echinoderms,
and require reduction by percentages that probably range at least 33 to
75%. His average valuations for large areas all concern the bottom
fauna outside the 6-meter limit, in depths ranging from 10 meters up-
wards. The average valuation obtained for the Thisted Bredning, years
1910—1916, with an area of 65,000,000 m.2 (=16,055 acres) was 3,298
lbs. per acre, rough weight, which would figure down by the percentages
mentioned to 800 to 2,200. The Nissum Bredning averages for 110,-
000,000 m.2 (27,170 acres) was somewhat lower, 2,418 lbs., which would
stand with deductions of 33 and 75% at 600 or 1,600 lbs.
Petersen's figures for restricted Mytilus and Modiola (a mollusk re-
lated to Mytilus) communities — 167,556 and 92,036 lbs. per acre, or 83
and 46 tons, respectively, the first in 2-meters depth, the second in 28
meters — by far exceed anything that has been reported elsewhere, so far
as we know, for sea or land crops. The figures in the case of the Mytilus
haul are equivalent to 552.9 ounces per square yard, or to 0.42 ounce
per square inch of bottom area : and those for Modiola, to 303.7 ounces
per square yard, or 0.23 ounce per square inch. These figures com-
pare with about 10 ounces per square yard (3,029 lbs. per acre), the net
average weight* of the Illinois River channel collections of 1915 between
* Shells of Mollusca deducted.
439
Copperas Creek dam and Havana. The Mytilus taken by Petersen, as
shown by the photographed heaps as they fell out of the bottom sampler,
were lying upon each other on the sea bottom.
Marine Bottom Fauna Valuations (Petersen, 1911 — 1918)
averages, pounds per acre*, large areas
Depth
Acres
Pounds per acre
rough weight
Net weightf —
after deductions
33 and 75%
Thisted Bredning
over 10 m.
16,055
3,298
800—2,200
Nissum Bredning
over 10 m.
27,170
2,418
600—1,600
Petersen's Figures for Restricted Communities, Compared with Best Illinois-
River Channel, 1915
Depth
Pounds
per acre
Ounces per
square yard
Ounces per
square inch
Mytilus community
2 m.
167,556
552.9
0.42 Rough weight
Modiola community
28 m.
92,036
303.7
0.23
Rough weight
Average Illinois-riv-
er channel, Cop-
peras Creek dam
to Havana
3,029
10
Shells deducted
The Food of certain Small Bottom-Invertebrates in the River
Channel at Havana and the General Composition of
the Detritus
The results of microscopical examination of the stomach and gut
contents of a number of the commoner Gastropoda, Sphaeriidae, insect
larvae, and others of the small bottom animals of the channel opposite
Havana in July, 1914, suggested that settled limnetic plankton plays a
more important role in the food of the bottom fauna than seems to be gen-
erally recognized. The studies made call for a subdivision of the com-
moner small bottom-animals at that place into two main groups ; the one
depending principally upon plankton, and the other more largely upon
old detritus, though containing species that make considerable use of
* Pounds per acre calculated by us from Petersen's figures in grams per 0.25 m.2
t Our estimates.
440
plankton al§o. The specimens that fall clearly into the group of plankton-
feeders represented a rather wide range of families, including Sphaeriidae
(as represented by Sphaerium striatinum) ; young Unionidae, about one
year old; Bryozoa (Urnatella gracilis); Trichoptera (larvae of Hydrop-
syche species) ; Chironomidae (unidentified red larvae) ; and Planaria.
The stomachs of the Sphaeriidae and young Unionidae, though con-
taining principally settled limnetic plankton, held also small amounts of
fine dead detritus, as well as many living bacteria, apparently taken in
with the latter or with dead planktonts. The insect larvae (caddis and
Chironomidae) had enjoyed a clean feed of settled plankton, some of it
still alive when eaten. Some living bacteria were seen in the stomachs
of the caddis larvae. Species whose stomachs contained nothing but
dead detritus included a small Asellus and several tubificid worms. The
larger snails of the family Viviparidae (Campeloma subsolidum and
Vivipara contectoides) had eaten large quantities of loose detritus and
what appeared to be slime-clotted silt and organic detritus particles such
as is commonly found as a thin coating on the shells of the snails them-
selves and on other hard objects in the mud. Living bacteria, presumably
putrefactive or fermentative types, were exceedingly abundant in the ma-
terial in their stomachs. In small specimens of Vivipara and Campeloma,
on the other hand, diatoms and Chlorophyceae from the settling limnetic
plankton were not much if any less abundant than old dead detritus. At-
tached incrusting algae (Pleurococcus and Palmella types) were present
in the stomachs of all Viviparidae examined.
In going through samples of the loose bottom-ooze taken with the
mud-sucker (see Figure 6, page 372), I was struck with the fact that
limnetic plankton, principally diatoms and Chlorophyceae, was, next after
the flaky particles of decayed vegetable or animal matter that makes up
the dead organic detritus, the most abundant edible element in the ooze,
as far as could be determined, being decidedly more important in bulk
than normal bottom Protozoa and Rotifera. While bottom Ostracoda
were noted in the ooze they were relatively very rare, and limnetic
Copepoda, Cladocera, and Rotifera were represented only by fragments
or nearly whole carapaces or other chitinous parts.
The enormous numbers of bacteria seen swarming in and among
the flaky honeycombed particles of dead organic matter, and inside the
bodies of recently dead planktonts, suggest that these minute organisms
are themselves not an unimportant part of the food supply of both the
plankton- and detritus-eating bottom-animals. Both bacteria and minute
pale flagellates and ciliates were also very abundant in the interstices of
the slime-bound silt and detritus scum that envelops the upper surface of
the shells of a large portion of the living and dead snails. That this ma-
terial on their own backs is use.d as food by their fellows is apparently
proven by its presence in the stomachs as well as by the numerous
tracks of radulae identified in the mantle of scum on the backs of liv-
ing Vivipara and Campeloma examined.
441
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The Nitrogen, Organic Carbon, and other Oxidizable Matter
in the Bottom Muds of the River and Lakes below
Chillicothe, 1913—1914
1. Bottom Muds of the Illinois River Channel, 1913
Mud samples taken in the Illinois River channel between Chillicothe
and Kampsville in March and July — October, 1913, showed a rather wide
variation in the amounts of nitrogen present, as expressed in terms of
percentage of dry matter, but both in early spring and late summer
agreed in showing a higher average above than below Havana. In
percentage figures, as stated, five samples from above Havana, all
months taken together, averaged 0.306% nitrogen, or 61% richer than
the five samples taken on approximately the same dates at stations be-
low Havana, which averaged 0.189%. A lesser actual difference in
average nitrogen content is shown for the stations above and below Ha-
vana, when we take into account the specific gravity and the moisture
percentages of the samples and calculate average values of nitrogen by
weight for a given area to a depth (3 inches) supposed to approximate
the average depth of cut into the soft bottom by the dipper in taking
the samples. The average number of pounds of nitrogen to the acre,
figured in this way, was 1,918 for the stations above Havana; and only
26% less, or 1,417 lbs. per acre for the stations between Lagrange dam
and Kampsville, in which the specific gravity was visibly higher and the
moisture-content lower.
The organic carbon per acre figures out, both above and below Ha-
vana, at about 8 times the nitrogen, the averages standing at 14,111 lbs.
per acre for the stations above and 11,322 lbs. for the stations below
Havana. The total oxidizable matter (which includes both the nitrogen
and the organic carbon,- as well as various other substances, some of
them of a mineral nature), figured in the same way, averaged 48,345 lbs.
per acre to a depth of 3 inches in the river channel above Havana, and
31,869 lbs. per acre below Havana.
Compared with the stocks of nitrogen and total oxidizable matter
(dry weight) in the muds either above or below Havana, the total acre-
poundages of dry matter or nitrogen represented by the bottom inverte-
brate population of July — October, 1913, are extremely small, however
liberally figured. Taking the average bottom-fauna stocks of the river
between Chillicothe and Havana (the richest section) as 555 lbs. per
acre (see table, page 412), and assuming a dry-matter content of
about 10% and a percentage of nitrogen to dry matter of 7%, the dry
weight of the average stock of bottom fauna on one acre would stand
at 55 pounds, or about 1/900 of the dry weight of the total oxidizable
matter per acre in the channel mud of that reach, and the contained
nitrogen at less than 4 pounds, or about 1/500 of the total nitrogen per
acre.
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2. Bottom Muds of the Lakes between Copperas Creek Dam
and beardstown
Comparison of samples from the central portions of eleven lakes be-
tween the head of Clear Lake and Browning, May — October, 1914, on
the dry-weight percentage basis shows the shallow weedy lakes highest
in bottom nitrogen. The average of Flag, Seebs, and Stewart lakes
(Class III lakes) in terms of percentage of dry matter, was 0.39%, com-
pared with an average of 0.27% for seven of the deeper, more open lakes
of Classes I and II; and with 0.26% for Crane Lake — a lake of the very
shallow, very weedy type. The general average of all of the 19 mid-lake
samples from eleven lakes of 4 of the five classes (0.32%) was some-
what more than the average for the river channel stations above Havana
(0.306%) and nearly twice the river average below Havana (0.189%).
The general average of organic carbon in mid-lake samples was 3.89%,
comparing with 2.41% for the river channel above Havana, and with
1.51% for the channel below Havana. In organic carbon as in nitrogen,,
the shallow weedy lakes of Classes III and IV (with 4.30% and 5.19%)
averaged well above the deeper lakes of Classes I and II (with 3.67%
and 3.09%).
Both in Thompson and Quiver lakes, May — October 1914, the ni-
trogen and organic carbon figures were considerably highest in samples
from the shallower water, the percentages of average difference as be-
tween samples from under and over 6 feet in depth amounting in the
case of the nitrogen to over 30%, in both Thompson and Quiver lakes,
and in the case of the organic carbon to 15% in Thompson and to 52%
in Quiver.
Nitrogen and Organic Carbon in Muds, Thompson and Quiver Lakes,
May — October, 1914
Nitrogen
Per cent.
(in terms of dry matter)
Organic carbon
Per cent,
(in terms of dry matter)
Thompson
Lake
Quiver
Lake
Thompson
Lake
Quiver
Lake
Depth over 7 feet
Average
0.325
8*
0.320
4
4.83
8
3.46
4
Depth 1—6 ft.
Average
0.42*
7
0.440
4
5.56
7
5.27
4
All depths
Average
0.373
15
0.400
4
5.17
15
4.67
4
* The Italic figures give the number of samples.
447
Nitrogen, etc., in Mud of Illinois Valley Lakes, May — October, 1914
samples from middle, in deepest water
per cent. in terms of dry matter
-
Lake
Samples
Nitrogen
Organic
carbon
I.
Deeper
Clear— Mud
2
0.23
2.93
bottom-land
lakes
Liverpool
1
0.29
2.52
Thompson
4
0.32
4.83
Dogfish
1
0.30
3.46
Sangamon
1
0.22
4.86
Average (5 lake
averages \
0.27
3.72
II.
Deeper
Quiver
4
0.32
3.46
sand-beach
lakes
Matanzas
1
0.24
2.73
Average (2 lake
averages)
0.28
3.09
III.
Shallow,
Flag
1
0.52
5.48
weedy
lakes
Seebs
1
0.35
3.78
Stewart
1
0.31
3.66
Average
• «
0.39
4.30
IV.
Very shallow,
very weedy
lakes
Crane
1
0.26
5.19
General average,
0.32
3.89
448
Nitrogen, etc., in Bottom Muds, 1913 — 1914,
Illinois River Channel and* Lakes in Vicinity of Havana
Nitrogen
Organic
carbon
Total
oxidizable
matter
* +
*
t
*
t
River channel Chillicothe to
Kampsville
.247
100 1.87
100
6.32
100
River channel, above Havana
.306
123
2.41
128
7.71
121
River channel, below Havana
.189
76
1.51
80
4.25
67
Eleven lakes, vicinity of Ha-
vana, middle
.320
129
3.87
206
Thompson Lake, middle
.325
131
4.83
258
Thompson Lake, shore, 1 — 6 ft.
.428
173
5.56
297
Thompson Lake, all depths
.373
151
5.17
276
Quiver Lake, middle
.320
129
3.46
185
Quiver Lake, shore, 1—6 ft.
.440
178
5.27
281
Quiver Lake, all depths
.400
161
4.67
249
The Plankton and other Limnetic Oxidizable Matters carried
by the Illinois Eiver Channel at Chillicothe and Havana,
1909—1914
1. Stocks of Plankton Carried past Havana
September, 1909 — August, 1910
Calculations of the total plankton that passed Havana September,
1909 — August, 1910, from the silk-net figures of that year, increased in
* This column gives per cent, in terms of dry matter.
t This column gives percentage on base of Illinois River channel, Chillicothe
to Kampsville.
449
the average ratios found by Kofoid* to hold between silk-net and filter-
paper volumes in 1896 — 1899, show a figure for the twelve-month period
(200,477 tons) almost exactly treble the amount (67,750 tons) that was
carried in the average year just prior to 1900. Of the twelve months'
total about 89 per cent. (179,916 tons) was accounted for during the
four months of the spring season, March to June inclusive, during which
period 1,474 tons passed every twenty-four hours. The 14,025 tons that
passed during the five months July to November inclusive, made up only
6.9 per cent, of the total for the year, but this amounted to ninety-one
tons every twenty- four hours, and was enough if all settled to the bot-
tom to supply 1,698 pounds per acre for every acre in the river below
Copperas Creek dam at the average gage of that season and year (7.8
ft., Havana). The December — February plankton (6,536 tons) was less
than half that of July — November, and only 3.2 per cent, of the total.
The full twelve .months' total, over 400,000,000 pounds, amounted to
24,279 pounds per acre for each acre of the approximate acreage in the
river below Copperas Creek dam at recent under-bank-full stages (8 ft.,
Havana) ; or to nearly a hundred times the wet weight of the total
bottom-fauna stocks of July — October, 1915, shells deducted, between
Copperas Creek and. Grafton (4,277,351 pounds). The dry weight of
this plankton at two to five per cent. (8,000,000 to 20,000,000 pounds)
was twenty to fifty times the estimated dry weight (at 10 per cent.) of
the total bottom stocks of 1915 below Copperas Creek (427,735 pounds).
Complete figures for the plankton stocks produced in the full 120
miles between Havana and Grafton would doubtless also include, in ad-
dition to the Havana figures, new stocks of no small size added on the
way down stream, both as a result of normal multiplication and lake and
other backwater contribution. I do not take the fact that all of our
down-stream plankton series between 1899 and 1910 showed a large de-
crease in volumes southward of Havana as ruling out the inference of
continued though hidden increase, at a rate merely slower than the rate
of decrease due to consumption and settling. The average time of pas-
sage between Havana and Grafton was 6.7 days at the average gage of
July — November, 1909 (7.81 ft., Havana), and was 4.82 days at the
average gage of March — June (Havana, 12.04 ft.). During upward
pulses, rates of increase in plankton volumes (c.c. per m3) were several
times recorded both by Kofoid and the writer for the river channel at
Havana and for Thompson Lake, both in spring and autumn months,
1896 — 1910, that amounted to over 25 per cent, in one day; while in ex-
treme cases the increases ran to 60 to 70 per cent, in a single day, or
400 to 500 per cent, in a week.
* Bui. 111. State Lab. Nat. Hist., Vol. VI., Art. II., 1903, pp. 552-554.
450
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2. Stocks of Total Nitrogen and Nitrates in the River Channel
at Chillicothe, 1914 — 1915
Comparison of the plankton figures obtained at Havana September,
1909 — August, 1910, with the total nitrogen and nitrate figures for
Chillicothe, March, 1914 — February, 1915, does not suggest that plank-
ton production in the river between Havana and Peoria has been at all
in danger of limitation by the nitrogen supply at any season during re-
cent years. The total nitrogen that passed Chillicothe in the twelve
months (67,722 tons) was sufficient, if all metabolized without loss, to
produce more than ninety times the actual stocks of plankton that
passed Havana in the year 1909 — 1910 (based on a dry-matter per cent.
= 5; nitrogen per cent, in dry matter = 7) ; while the stock of unused
nitrogen in the form of nitrates (22,345 tons) was capable of producing
under the same conditions more than twenty times the total plankton
that actually passed Havana in 1909 — 1910. At the dry matter and ni-
trogen ratios assumed, only about 1,431,983 pounds out of the total
of 35,444,859 pounds of nitrogen that passed Chillicothe in the year
1914 — 1915 would be accounted for as nitrogen in the form of living
matter in 400,000,000 pounds of plankton (the approximate amount that
passed Havana September, 1909 — August, 1910).
If we could distribute the total nitrogen that passed Chillicothe
over a river acreage of 26,782 acres (the estimated acreage below Chilli-
cothe at about 8 ft., Havana, the average gage of July — November, 1910
— 1914), we would have 2,442 pounds per acre in the March — June pe-
riod; 1,495 pounds per acre July — November; 1,119 pounds per acre De-
cember— February; and a total of 5,057 pounds per acre for the year.
The nitrates, similarly distributed with correspondingly lesser poundages
for the separate seasons, would amount to 1,668 pounds per acre for the
twelve months on the same acreage.
The Peoria discharge data entering into the various tables following
are the rating-table figures of Jacob A. Harman, as published in the
special Report of the Illinois State Board of Health on Sanitary In-
vestigations of the Illinois River, 1901, and more recently used by Alvord
and Burdick in the Report of the Rivers and Lakes Commission on the
Illinois River and its Bottom-lands, 1915. These figures are consider-
ably higher than recent figures of the U. S. Geological Survey, which we
did not have at hand, except in fragmentary form, when the manu-
script for the present article was being prepared.
452
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455
3. Total Stocks of Oxidizable Matter in the River at
Chillicothe, 1914 — 1915
Not only the plankton, but in addition all the other oxidizable matter
carried in the stream-flow, whether suspended or dissolved, may be re-
garded as potential detritus or as potential microorganisms, some portion
of which, in some form or other, may be useful as food to the bottom
animals or to the organisms on which they themselves feed somewhere in
the course of the stream below the sampling point. If the total oxidiza-
ble matter at Chillicothe 1909 — 1914 was in about the same ratio to the'
total nitrogen as in 1900 — 1902 (about ten times total nitrogen in the
winter and spring months, and seven to nine times the nitrogen figures
in midsummer and autumn), we would have had passing Chillicothe in
the entire year, March, 1914, to February 1915 a total of 617,137 tons, or
over 1,200,000,000 pounds total oxidizable matter, dry weight, or some
sixty to a hundred and fifty times the total dry weight of the plankton
that passed Havana in the twelve months September, 1909, to August,
1910 (eight million to twenty million pounds). If this enormous total
load could be settled out and apportioned equally to the approximate
26,780 acres of river between Chillicothe and Grafton at gage 8 ft., Ha-
vana, each acre would receive in the course of the year 46,086 pounds,
an average equal to more than seventeen hundred times the average dry
weight poundage (about 10 per cent.) of bottom animals per acre
(twenty-six pounds) found in the summer of 1915 between Chillicothe
and the river's mouth. The employment of vertical instead of surface
chemical samples for the determination of loss on ignition would with
little question, also, show still higher values of total oxidizable matter
than those here figured, particularly in seasons of recession from flood,
when the dead suspended organic matter increases heavily in concentra-
tion from the surface downward. (See table on p. 456.)
4. The Portion of the Plankton Settled out or Consumed
Basing the computations on percentage decreases in silk-plankton vol-
umes (c.c. per m.3) between Havana and Grafton in June and August
1910, and on rates of increase in discharge between Havana and the
mouth of the river in the spring and midsummer months, but taking no
account of normal multiplication, there is found for the nine-months
growing season, March — November, 1909 — 1910, a total loss of plank-
ton in the 120 miles below Havana of 243,503,139 lbs., or almost exactly
two thirds of the total stocks that passed Havana during the period
(387,883,000 lbs.). The dry weight of this lost plankton at 5% (12,-
175,156 lbs.) amounts to nearly 30 times the dry weight, estimated at
10%, of the bottom animals found in 1915 in approximately the same
reach of river in which the loss occurred (total bottom-fauna stocks
Copperas dam— Grafton, 1915, 4,277,350 lbs; dry weight at 10%, 427,-
735 lbs.).
456
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That the greater part of the plankton lost, or all of it, was settled
out or consumed by larger organisms, rather than that it perished be-
cause of any failure of the food supply (particularly nitrogen), is forci-
bly suggested by two or three considerations : that the losses took place
at the greatest rate during the hot season, when the current was least and
settling easiest, the rate of loss in August 1910 being 98% ; and that in-
stead of there appearing any evidence that the losses were due to dim-
inution in food, both the total limnetic nitrogen and the. nitrogen in the
form of nitrates increased down-stream both in the spring and midsum-
mer— autumn months in 1914, the nearest year for which we have nitro-
gen figures. I note here that incomplete studies on the succession of
Algae, Protozoa, Rotifera, and Entomostraca in some of our down-
stream series of plankton-catches suggest that a good part of the loss in
plankton below Havana in the spring months during rising pulses of En-
tomostraca may be due to internal consumption, within the plankton
population itself. In May, 1899, in fact, these four groups of micro-
organisms showed a progression in reaching their maximum abun-
dance, each at a station farther down stream. In the circumstances the
presumption seems strong that each pound of Cyclopidae or Rotifera
taken near the mouth of the river represents several pounds of smaller
plankton species eaten farther up stream. (See tables, pp. 458, 459.)
5. Coincidence of Richer and Poorer Plankton and Bottom-
Fauna Reaches in the River below Chillicothe
The fact that there are shown, on a basis of the plankton and bot-
tom-fauna figures (1899 — 1915), such close coincidences between the
location and extent of the richer and poorer plankton and bottom-fauna
reaches between Chillicothe and the mouth of the river is not, I think, to
be taken too quickly as in itself dependable evidence that the bottom
fauna is to any certain and large extent a simple function of the vol-
ume or weight o*f plankton above it. Not only, however, does it appear
that both in its bottom fauna and its plankton stocks the sixty odd miles
of low-sloped river channel between Chillicothe and Havana is far
richer on the average than the lower river reaches, but the decrease
down stream, on a broad scale, is in each case found to be progressive,
and in fact in substantially similar ratios, if the comparison is made with
the midsummer plankton figures. (Table, page 460.) The finding, on the
contrary, in August 1913, in a local section of low-sloped channel in the
lower river, of a rich plankton-consuming population of Sphaeriidae
that was apparently not far from as rich as the best found in 1915 in
the middle Illinois Valley district suggests that the very general lack
of a suitable substratum for small Mollusca in the channel of the Illi-
nois below Lagrange may have more to do with the decrease of the
bottom fauna in the lower river than the decrease in the stock of plank-
ton above it. Other influences that may have some bearing on the aver-
age very poor showing made by the bottom fauna in the lower river in
1915 will be taken up farther on.
458
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461
6. The Plankton of Thompson Lake, 1909 — 1910
As shown by volumes per cubic meter of silk plankton, based on
vertical samples, the middle of Thompson Lake and the river channel
at Havana averaged nearly the same in plankton content during the four
months March — June, 1910 (Thompson, 12.77 c.c. ; river, 13.98 c.c.) ;
while in the July — November period of five months Thompson Lake
(5.21 c.c.) averaged about six times as rich as the river (0.87 c.c).
Expressed in terms of pounds per acre to a depth of one meter, these
volumes of plankton amount to around 114 lbs. for the lake and 124 lbs.
for the river in the March — June period, and to 46 lbs. for the lake
and 8 lbs. for the river in July — November. If these quantities of silk
plankton are multiplied, both in the case of the river and the lake, by the
Kofoid silk-filter-paper ratios for river samples, 1897 — 1899, the pound-
ages for March — June would be about twice those just given, and
for July — November about four times those figures. On the other
hand, if depth is taken into account, and total amounts of plankton
standing over an acre in the river and the lake to the full average depth
at the collecting station are figured, the river acre in March — June will be
found to have more plankton standing over it at a given time than an equal
area in the central portion of Thompson Lake ; and in July- — November,
about half as much, instead of only one sixth as much, as an acre in the
lake.
Plankton Thompson Lake and Illinois River, Havana, 9 months,
March— November, 1909—1910
Gage,
Havana
average
Depth
coll. sta.
feet, av.
Depth
coll. sta.
meters, av.
Silk
plankton
c.c. per m3
Silk
plankton
lbs. per acre
to depth
1 meter
March — June incl.
Thompson L.
12.04
12.23
3.7
12.79
114
Illinois River
12.04
22.23
6.7
13.98
124
July — November incl.
Thompson L.
7.81
8.00
2.4
5.21
46
Illinois River
7.81
18.00
5.4
0.87
8
462
General Comparison of the Illinois River and its Connecting
Lakes in the Food Resources of a Fishery and in
Fish Output
Bottom and Limnetic Nitrogen, Plankton, etc.
In the fact that the Illinois Valley lakes, only in a lesser degree than
the river itself, are in the spring or later flood-seasons of all but very ex-
ceptional years open to receive the sewage-laden water from the upper
Illinois River and the Chicago Sanitary Canal, they differ materially
from the isolated glacial type of lake and from ponds or other waters
which are closed throughout the year to outside sources of nutriment.
Such supplies as the river lakes receive, they are able to retain in great
measure when their outflow is reduced to little or nothing by the falling
of the water levels, but the acquired resources of the river are contin-
ually drained away by the current, these losses being especially heavy
when the bottom sediments are being stirred up and scoured out in times
of flood. Hence the river, as we have seen, is not able to accumulate
and hold, even in the reach of extremely low-slope between Copperas
Creek dam and Lagrange, surplus stocks of these substances and the resi-
dues from their decay as large as the stocks found in the lakes, whether
in their deeper open, or in their weedy littoral portions ; while in the
relatively swifter channel below the Lagrange dam the difference is still
further emphasized. So far as the plankton alone is concerned, the sur-
plus stocks on hand at a given time per cubic meter of water in Thomp-
son Lake in 1909 — 1910 exceeded those in the richest part of the river
at Havana, opposite, at whatever season, with the percentage of differ-
ence in favor of the lake largest during the more critical season of low
productivity, July — November. .
That the central Illinois Valley lakes are also to a considerable ex-
tent their own furnishers, through the growth and decay of shore vege-
tation, of their permanent stocks or organic food-materials, is suggested
by the size of the annual crops or aquatic vegetation, some of which is
rooted, in their shallower zones ; as well as by the fact that the stocks of
nitrogen, organic carbon and other oxidizable substances in the upper
layer of bottom soil are appreciably larger in the weedy littoral than in the
deeper open water. The river, whether in the Havana district or above
or below, has as offset extremely little weedy shore, where rich stocks
of similar kind can originate and decay, or where permanent lodgment
can be furnished for settling suspended organic matters carried in from
points up stream.
Bottom and Shore Fauna
In the case both of the plankton and of the various other food sub-
stances directly or indirectly usable as food by the bottom and shore ani-
mals, our data, as far as they go, point clearly to the presence at all
463
times, both in the river and in the lakes, of surplus stocks of a size far
more than sufficient to supply the immediate needs even of vastly richer
bottom and shore populations than we found in 1914 — 1915. But though
the river, at least in the region of low slope between Chillicothe and Ha-
vana, could thus theoretically produce as large poundages of bottom and
shore fauna as the lakes, or even larger, the figures for stocks on hand
in the two years mentioned, as well as other evidence, tend rather to
prove that the lakes are over their average acreage the better producers,
and that their richest fauna is developed in the weedy littoral, where also
occur the largest deposits of nitrogen, organic carbon, and other oxidiza-
ble matters.
As the margin between the bottom and shore fauna stocks on hand
in 1914 — 1915, even in the most productive lake and river areas, and the
food requirements, in kind, of a normal fish population, as of 1908 and
neighboring years, seems clearly to be very much smaller than that be-
tween the supplies and the needs of the bottom and shore fauna itself,
it may- be supposed that figures for stocks on hand after four or five
months' feeding by fishes can not be accepted as they stand, quite as
confidently as plankton and nitrogen figures for use as an index of
actual total productivity. If this is the case, and if it is also true, as we
have reason to think, that the lakes rather than the river are not only
the favorite feeding-grounds of the greater part of the large bottom-
feeding fishes during the 9-months growing season but also the largest
producers of fish flesh, then we should expect that complete figures for
total annual yield of bottom and shore invertebrates for the river and
lake acreage in the Havana district would show a yet greater difference
in favor of the lakes than is shown by the figures of stocks on hand as
of July — October, 1914 — 1915. A further point in favor of the lakes
is the fact that the very heavy bottom-fauna poundages of the river
channel just above Havana consist largely of heavy-shelled snails, which
we can not believe are easily made use of as food by any but the largest
bottom-feeding fishes. Looked at in this way, the richest river valua-
tions may represent accumulation in the presence of light feeding ; while
the lower poundages of bottom animals in the lakes opposite may be
looked upon as residues from originally much larger stocks, fed down to
a closer point than the river stocks, in consequence both of a relatively
greater size-availability and of their location within the main-feeding
range.
Fish Yields
On a plain acreage basis the total river acreage, at a gage of 10 feet,
Beardstown*, between La Salle and Grafton, with equal productivity as-
sumed in both river and lakes, should in 1908f have supplied around
18% of the total fish yield of that year, and the lakes about 82%. In
* Gage selected by Alvord and Burdick as that prevailing- on an average one
half of the year, 1900 — 1913.
t Last year for which we have full figures for fish yields.
464
the same year the river between Copperas Creek dam and Lagrange dam,
where the lake acreage is largest relatively to the total, should have
furnished about 10% of the total fish yield; the river between La Salle
and Copperas Creek dam, about 17% ; and the river below Lagrange,
about 37%. That the river and lake yields of fish per acre are not equal,
however, is suggested with considerable force by more than one consid-
eration. The first of these is the fact that in all the recent years for
which we have records the largest poundages of fish per acre have been
taken in the reaches with the largest quotas of connecting lake-acreage.
Taking the year 1908 as an illustration, and using the figures for sep-
arate shipping points obtained by the Illinois Fish Commission in that
year, we find for the 59.3 miles of river and lakes between Copperas
Creek dam and Lagrange dam, with about 90% of its acreage consisting
of lakes and ponds, an average fish-yield per acre for water levels pre-
vailing half the year, of 178.4 pounds; for the 87 miles from La Salle
to Copperas Creek dam, with about 83% lakes, 130.4 pounds; and for
the lower 77 miles, Lagrange to Grafton, with around 63% lakes, only
69.8 pounds.
If, again, we seek to reach conclusions concerning fish yields for
the central Illinois Valley district from the bottom- and shore-fauna
data of 1914 — 1915 we can only suppose that the average yield of the
river per acre in recent years between the Copperas Creek and Lagrange
dams (with 705 lbs. bottom fauna average) has amounted to less than
half the average yield of the lakes opposite (with 1,447 -f- lbs. bottom-
and weed-fauna average). Or, to put it another way, while the river's
quota of the total fish catch in this reach on a plain acreage basis in 1908
was 10%, its capacity on a basis of the bottom- and shore-fauna figures
of 1914 — 1915 uncorrected, stands at about 5% of the total.
That both the river and the lake yields of fish per acre have been
lower in recent years in the reach above Copperas Creek dam and in the
reach below Lagrange than in the district between, is suggested both by
our bottom-fauna data from the river and by such incomplete figures as
we have from Peoria Lake and Meredosia Bay (1913 and 1914), and
also by the fact that the differences in fish yield per acre in 1908 between
those two reaches and the Havana section are much greater than the
difference in the ratios of lake to total acreage. That, however, the per
cent, decrease in fish-yield in the lakes in these two reaches is less than
the decrease in the river may perhaps be accepted as circumstantially
proven by the greater decrease in the river bottom-fauna figures than in
the figures of fish yield themselves.
465
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467
Fish Catch, Illinois River and Lakes, 1908
(III. Pish Comm.)
La Salle to Copperas Creek dam
La Salle to Hennepin
520,000 lbs.
Henry to Lacon
852,000 "
Chillicothe
350,000 y "
Peoria
2,800,000 "
*Pekin (one half)
1,700,000 "
Total
6,222,000 lbs.
Copperas Cr. dam to Lagrange dam
*Pekin (one half)
Havana
Bath
Browning
Beardstown
Total
1,700,000
3,800,000
1,900,000
1,700,000
1,950,000
lbs.
11,050,000 lbs.
Lagrange dam to Grafton
Mered'osia
Naples to Pearl
Kampsville to Grafton
Total
684,000 lbs.
409,000 "
905,000 "
1,998,000 lbs.
Grand total
19,270,000 lbs.
* Pekin catch divided between adjacent reaches because of heavy fishing- by
Pekin crews in Spring Lake.
Bottom- and Shore-Fauna Valuations, 1915, in Terms of Months'
Supply for Annual Increment in Fish-Weight
of 150 Pounds per Acre
How close to a critical minimum, from the point of view of the fish-
ery, the stocks of bottom invertebrates in the lower Illinois River had
dropped in July — October, 1915, after 5 to 8 months' feeding, is most
clearly seen after we have changed the bottom-fauna valuations into
terms of months' supply of food for an annual yield of fish somewhat
nearly equal to the average for the year 1908 on the acreage estimated
to prevail during half of the year. In the tables next following, these
calculations are shown as they come out for an annual weight increment
of 150 lbs. per acre, the year's feeding being completed in 9 months
(March — November), animal food only being used, and an average
consumption of five pounds of bottom and shore invertebrates (shells
of mollusks deducted) for one pound increase in fish weight being as-
sumed. The feeding ratio (5:1) adopted is the estimate of Walter* for
carp and carp-like fishes, living on wild animal food, and is close to the
* Die Fischerei als Nebenbetrieb des Landwirtes u. Forstmannes. 1903.
468
ratios estimated by Otterstrom* and Kronheimy for trout fed on raw fish
or "mostly animal food". The rate of consumption of bottom (or shore)
invertebrates per month for the nine-months "year" works out at about
83 pounds :
150 X 5
= 83.3
9
Expressing the bottom- and shore-fauna valuations of 1915 in mul-
tiples of the average monthly consumption rate, we find that in July —
October of that year there were 120 miles of the Illinois River below
Havana whose average supplies of free-living bottom-invertebrates were
sufficient to last at such a rate only 30 days or less beyond the date of
collection ; and 77.5 miles below Lagrange dam in which there were
sufficient stocks to last only 3 days. The much richer stocks in the river
above Havana, in" spite of the exceedingly low valuations in the lower
river, were sufficient to bring up the average supply for the entire 180.5
miles between Chillicothe and Grafton to a figure of 3.1 months — which
was also the average for the 60.5 miles between -Chillicothe and Cop-
peras Creek dam. In the reach of 59.3 miles between Copperas Creek
and Lagrange, where an average supply sufficient for 8.5 months was
found, there was a short stretch of 16.8 miles (immediately above Ha-
vana) where the stocks were sufficient to last for over 30 months, but a
relatively much greater part of the bottom fauna in this locally very rich
section was made up of large heavy-shelled Mollusca than was the case
in any other part of the river.
In contrast with all of these river figures except those for the 16.8-
mile reach between Copperas Creek and Havana, the average stock of
twelve lakes between Copperas Creek and Lagrange in July — October,
1914 — 1915, included a three months' supply of bottom fauna only for
the whole acreage, a minimum^ of 25.5 months' supply of shore animals
living above the bottom in the weedy acreage within the 4-foot line, and
a combined average supply of bottom- and shore-animals sufficient for
17.4 months. (See table, p. 469.)
Supplies of bottom animals that were well above the average of all
the lakes studied, were shown by the Class I and Class II lakes (of the
type of Thompson and Quiver respectively) : average of five deeper
bottom-land lakes, 4.2 months ; average of two deep, sand-beach lakes,
10.2 months. Thompson Lake in 1914 had in August to October a 6.5
months' supply of bottom invertebrates over its entire acreage, and a
25.7 months' supply of weed animals in the 1 — 4-foot zones — or a com-
bined average supply, on a rough acreage basis, sufficient for 20.8
months. The low v rating of bottom- fauna stocks in the very shallow
weedy lakes, such as Flag, Duck, Dennis, (0.6 to 1.1 months' supply),
* Fiskerei beretning, 1911, pp. 244 — 254.
t Bibl. der Gesamten Landwirtschaft, Bd. 34, 1907.
% "Weed fauna" catches cover the upper 9 inches only.
469
was of little importance by comparison with the very high weed-fauna
figures from these lakes, the combined bottom and weed fauna averages
(if Crane Lake be excepted) apparently including a supply sufficient for
not less than 25 to 30 months. (See table, p. 470.)
Bottom and Shore Fauna as Food for Fishery
1. Illinois River, July — October, 1915
Italic figures=months' supply, at 83 lbs. per month, for 9 months' growing
season for fish-weight-increment of 150 lbs. per acre, feeding ratio 5:1.
Miles
Bottom fauna
all-zone av.
lbs. per acre
Months' supply
remaining on
date of col-
lection*
Chillicothe — Copperas Cr. dam
43.7
264
8.1
Copperas Cr. dam — Lagrange
59.3
705
8.5
Copperas Cr. dam — Havana
16.8
2,693
824
Havana — Lagrange
42.5
83
1.0
Lagrange — Grafton
77.5
10.4
0.1
Chillicothe — Grafton
180.5
261
8.1
Hypothetical Fish-Yields for the River and Lake Acreage be-
tween Copperas Creek Dam and Lagrange, on Basis of Bottom-
and Shore-Fauna Stocks of July — October, 1914 — 1915
In the table on page 471 are shown figures representing the po-
tential value in fish, at the Walter ratio (5:1), of the bottom- and
shore-fauna stocks remaining unconsumed in the central rich district
between Copperas Creek dam and Lagrange July — October, 1914 — 1915,
after 5 to 8 months of feeding. The total hypothetical yield of the un-
consumed stocks of food thus figured (16,103,580 lbs. of fish, from
80,517,900 lbs. bottom and shore animals), is greater by about 50% than
the actual fish catch of 1908 (a banner year) in the same district. Of
this total, 831,900 lbs., or 141 lbs. per acre, accrues from about 6,000
acres of river, bearing over 4,000,000 lbs. of small bottom animals ; and
15,271,680 lbs., or 289 lbs. per acre, from about 52,000 acres of lakes and
other backwaters, bearing not less than 76,000,000 lbs. of small bottom-
and shore-animals, of which over 60,000,000 lbs. comes from the upper
levels in the shallower, more densely weeded acreage.
* Dates of collection, July — October (after 5 to 8 months' feeding).
470
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472
The Reproductive Rate of the Bottom Animals
Petersen, writing of the bottom fauna of the Danish fishing grounds,
1911 — 1918, has expressed the opinion that the bottom animals at least
reproduce themselves in weight each year. This conclusion was based
by Petersen on the observed fact that from year to year, on the average,
similar quantities of bottom animals are found over the same areas, along
with similar populations of bottom-feeding fishes. It is perhaps true that
more regularity in this respect might be expected in sea-bottom than in
the bottom muds of our relatively. shallow inland rivers and lakes, which
are subject to extremes of temperature; to floods and consequent wash-
ing and filling ; to disturbance by seining and artificial dredging for navi-
gation channels ; and to other unfavorable influences.
With more particular reference to growth rates in small bottom
Mollusca, I note that Petersen (1911) remarks that a small Sphaerium-
like form, Abra sp., reproduces its weight several times in a year ; and
that F. C. Baker recently observed of very young specimens of the genus
Ampullaria, from Ceylon, that they doubled in size in an aquarium in
3 months.
Body weights taken by us of a series of 3 to 63-month specimens of
one of the commonest snails from the Illinois River and its connecting
lakes, Vivipara contectoides, all from late July collections, 1913 — 1914,,
indicate an average increase in body weight in one year running from 63
to 100% for the different age-groups studied.
Growth of Vivipara contectoides,* Havana
Age, months
(estimated)
Years
(estimated)
Maximum
length of
shell, mm.
Body
weightf
mg.
Increased
weight
next
12 months
mg.
Per cent,
increase
next
12 months
3 ca.
0.25
11.5
160
132
82
12—15
1.00—
13.0
292
186
63
24—27
2.00—
15.0
478
438
91
36—39
3.00—
20.0
916
800.
87
48—51
4.00—
27.5
1,716
1,734
101
60—63
5.00—
. 39.0
3,450
The possibilities of -multiplication of this particular snail, if left to
itself, are even better shown by an analysis of a collection from Seebs
* All weights are of late July specimens, 1913; 3-months' specimens, evidently
from spring- brood same year; not possible to determine whether specimens one
year and up were from spring or midsummer broods.
f Corrected for loss in alcohol.
473
Lake containing 100 specimens, ages 3 months and upwards, taken in
late July, 1913. Out of 32 specimens over 32 months old, which were
capable of 87 to 101% increase in body weight in the next 12 months,
30 carried advanced embryos (midsummer brood) totaling 460.
Figuring the average increase in body weight of young and adult
age-groups in the next 12 months at 82.2%, the total body weight of the
entire collection (without embryos), which was 72.286 grams at date
of collection, would be approximately 131.7 grams one year later. Twelve
months' growth in the 460 embryos, assuming that all lived, might be
expected to amount in the average individual to at least 4/5 of the aver-
age body-weight of 12 to 15-month specimens (see table), or 233.6 mg.
each, making the total weight-increment in the 460 embryos in 12 months
107.4 grams. Adding the increase in the embryos and that in the young
and adults to the original total body-weight of the collection (72.3 grams)
we have, 12 months after date of collection, without making any allow-
ance for increase from a spring brood, a hypothetical total weight of
239.1 grams, or 3.3 times the weight with which we started.
Possibilities of Growth of Vivipara contectoides
(based on collection from seebs lake, JULY 25, 1913)
Age groups (estimated1)
Av. rate increase in
body-weight next
12 months
Advanced embryos
(of midsummer brood)
32 specimens over 27 months
6 'specimens, 24 — 27 mos.
22 specimens, 12 — 15 mos.
40 specimens, 3 — 4 mos.
87—101 %
91%
63%
82%
460 (in 30 specimens)
Total, 100 specimens
82.2%
460
Gross weight of collection, 94.0 grams.
Body weight (corrected for loss in alcohol) 72.3 grams
Increase in bocly-weight next 12 months, at 82.2% 59.4
Increase in weight of embryos, next 12 months, at 233.6 mg.* each 107.4
Total 239.1 grams
=3.3 X original weight.
* Equals % of weight of 12 — 15-mo. specimens (preceding- table).
474
Changes in the Quantity of the Bottom-Fauna Stocks
between 1913 and 1915
Various conditions or agencies besides any heretofore mentioned
are doubtless capable of effecting local or temporary changes in the com-
position and weight of the bottom and shore animals either in the river
or the lakes. Among those peculiar to the river may be mentioned the
occasional scouring effect of floods in the regions of steepest slope, re-
sultant natural filling at points farther down stream, and the cutting away
of the river floor by artificial dredging for channel improvement. In the.
lakes in which the heaviest commercial fishing is carried on, injury may
be done to the bottom animals in the fall of the year by the heavy tackle
used. Either in the river or in the backwaters variations of importance
in the size of the bottom-fauna stocks may doubtless result from changes
in the size of the population of bottom-feeding fishes, these variations
being in the direction either of decrease or accumulation. Mortality
from other unknown causes no doubt occurs at times, as seemed to be
the case with the larger snails in Quiver Lake between July 1914 and
July 1915. Of water pollution I note that this was not anywhere an im-
portant cause of mortality in the river bottom-fauria below Chillicothe up
to and including 1915.
Comparison of such data as we have for the season of 1913 with
the more complete results obtained in 1915 indicates generally a quite
satisfactory correspondence both in average composition and size of the
bottom- fauna stocks in the longer reaches of river channel between
Chillicothe and the Kampsville dam, both series of collections bringing
out clearly the contrast between the more productive reaches of channel
above Havana and the decidedly poorer stretches below. The most
important single point of disagreement between the 1913 and 1915 river-
figures- concerns the finding in 1913 in the lower 30 miles, where in 1915
the average channel stocks of bottom animals were no larger than any-
where else in the lower 75 to 100 miles, of a rich local fauna of Sphaerii-
dae which apparently compared very well with the best found in the
rich Havana district. The presence, only locally, of so rich a bottom
population seems to imply the existence in that part of the river of
an adequate food supply, and is doubtless sufficiently explained other-
wise by its occurrence in a region of less than average slope and velocity
and more favorable conditions for sedimentation than are found in most
of the lower 100 or more miles of channel. For its disappearance be-
tween 1913 and 1915 no certain explanation offers. I note, however, that
it is in this wider, and on the average swifter portion of the channel that
bar formation is most frequent in the Illinois and that dredging opera-
tions for channel maintenance are oftenest carried on. It is also in this
part of the river, where for more than 70 miles the far greater portion
of the bottom-land lakes had been leveed and drained before 1915, that
sudden depletion of sporadic bottom-animal populations might most
475
easily be accomplished by the waves of large carp and buffalo that ad-
vance up the river every spring, and that have in recent years been
practically confined within the bank limits of the river itself for feeding
range until they have reached a point near or above the Lagrange dam.
The last hypothesis as an explanation of this single circumstance, and,
as well, of the comparative poverty of the bottom fauna of the entire
lower 77 miles of the river, receives some support from the fact that
while in 1915 the bottom- fauna stocks between Lagrange and Grafton
dropped nearly to the vanishing point, both in the channel and shore
zones, between Lagrange and Havana, where there was still a large lake-
acreage open to the river, the important decrease in the bottom fauna
over Havana district figures was to be seen only in the channel valua-
tions and was apparently, for the most part, explained by the character
of the channel bottom.
Only two of the twelve lakes in the Havana district (Thompson and
Quiver) were examined both in 1914 and 1915 with sufficient complete-
ness to permit a fair comparison of their stocks of bottom animals as of
these two years. While there was an increase of 60% in the average
quantities (by weight) in the deeper open water of Thompson Lake from
1914 to 1915, the changes in the shallower zones, and in both the deeper
and shallower areas in Quiver Lake, were in the direction of decrease,
Bottom-Fauna Stocks, Illinois River Channel, 1913 and 1915,
( July — October)
Reach
Average number
individuals per
collection.*
1913
Average number
individuals per
sq. yard
1915
Average pounds
per acre
1915f
Chillicothe to Copperas Cr.
darn
101
10%
203
33
239
Copperas Creek dam to
Havana
280
6
880
16
3,029
Havana to Lagrange
22
8
15
16
22
Lagrange to Kampsville
29
15
17
9
7
Kampsville to Grafton
§
9
28
7
6
* All hauls with ordinary iron dredge, with coarser mesh bag than in 1915.
t Not figured for 1913 because of less certain quantitative value of 1913-series
of collections.
t The Italic figures give the number of collections.
§ Five hauls at the foot of Six Mile Island yielded an average of nearly 1,000
specimens of Musculium transversum per collection ; other hauls, poor.
476
the percentages ranging from about 30 to 70%. In Quiver Lake the
principal part of the decrease resulted from a heavy falling off in the
small Mollusca, the unusual numbers of dead snails found everywhere
in the lake in 1915 seeming to point to some exceptional mortality from
unexplained causes.
Bottom Fauna Stocks, Lakes in Vicinity of Havana, 1914 and 1915,
( July — October)
Pounds per
acre, 1914
Pounds per
acre, 1915
Incr. or
deer, per
cent.
Notes
Thompson Lake
over 6 ft.
310
8*
496
8
+ 60% No essential change in
composition of fauna
1—6 ft.,
some vegetation
903
10
647
7
—28%
it It tt tt
1—6 ft.,
no vegetation
501
12
296
7
—40%
ft tt tt tt
Quiver Lake
over 6 ft.
2,805
15
803
3
—71%
tt It tt it
1—6 ft.,
some vegetation
388
11
158
—59%
Great decrease in snails
and increase in Chiro-
nomidae between 1914
and 1915
* The Italic figures give the number of collections.
477
DETAILED VALUATION TABLES
I. Bottom Fauna, Illinois River, 1915
1. Chilli cothe to Foot of Peoria Lake
8 Channel Collections, July 26 — 27 and Aug. 19
Chillicothe to Opposite Mossville
Number per square yard
Pounds per
acre
Campeloma subsolidum
17.3
51.9
Lioplax subcarinatus
39.7
88.2
47.6
244.1
Vivipara contectoides
28.2
141.0
Pleurocera sp.
3.0
3.6
Amnicola emarginata
2.5
trace
Ancylus sp.
0.7
trace
Physa sp.
2.5
143.7
0.5
70.4
Pisidium sp.
1.5
trace
Musculium transversum
135.3
67.5
Young Unionidae
1.2
2.4
Asellus sp.
0.2
trace
Small Oligochaeta
8.1
0.2
Leeches (small spp.)
14.3
26.6
2.4
3.1
Caddis larvae (small spp.)
0.2
trace
Chironomid larvae (smaller spp.)
3.7
0.5
Chironomid larvae (larger spp.)
0.1
trace
Total
258.5
317.6
478
16 Collections, 4- to 7-ft. Zone, July 26 — 27, Aug. 17 — 19, 1915
cllillicothe to opposite mossville
Number per square yard
Pounds per acre
Campeloma subsolidum
13.3
39.9
Lioplax subcarinatus
7.1
30.8
8.4
97.4
Vivipara contectoides
9.7
48.5
Pleurocera sp.
0.5
0.6
Somatogyrus sp.
0.6
0.3
Valvata spp.
4.3
0.2
Sphaerium stamineum
0.3
200.3
0.2
86.7
Musculium transversum
166.0
83.0
Musculium jayanum
.3.7
2.0
Pisidium species
25.4
1.0
Oligochaeta (small spp.)
21.0
Leeches (small spp.)
17.6
Asellus sp.
0.9
Hyalella knickerbockeri
7.5 •
Chironomid larvae (small)
9.9
Chironomid larvae (large)
5.3
Hexagenia, etc. (nymphs)
0.6
Caddis-fly larvae (small)
5.3
Agrionid nymphs
0.6
68.7
0.7
2.9
trace
0.3
1.3
•6.6
0.5
0.7
0.3
13.3
Total
197.4
479
9 Collections, 1- to 3-ft. Zone, July 26 and 27, 1915
Chillicothe to Opposite Mossville
Number per square yard
Pounds per acre
Lioplax subcarinatus
Vivipara coritectoides
2.2
5.5
7.7
2.6
27.5
30.1
Somatogyrus sp.#
Amnicola emarginata
Valvata spp.
Physa sp.
Planorbis trivolvis
Musculium transversum
Pisidium sp.
5.5
1.1
7.7
2.2
53.3
70.0
148.6
2.7
trace
0.4
2.0
1.5
26.6
28.0
61.2
Oligochaeta (small spp.)
Leeches (small spp.)
Asellus sp.
Chironomid larvae (small)
Agrionid nymph
Coleopterous larvae
Hyalella knickerbockeri
16.6
27.7
6.6
7.7
15.5
1.1
1.1
76.3
0.5
4.7
0.6
1.0
0.6
0.5
trace
7.9
Total
232.6
99.2
480
3 Channel Collections, July 28 and Aug. 19, 1915
Peoria Narrows
Number per square yard
Pounds per acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
Pleurocera sp.
3.3
0.6
3.3
16.0
23.2
9.9
0.7
16.5
19.2
46.3
Musculium transversum
1.0
1.0
0.5
0.5
Leeches (small spp.)
Caddis larvae (small spp.)
11.3
2.0
13.3
1.9
0.2
2.1
Total
37.5
48.9
4 Channel Collections, July 28 and Aug. 19, 1915
Lower Lake, Opposite Eagle Packet Landing
Number per square yard
Pounds per acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides*
Pleurocera species
26.0
37.0
48.2
23.5
134.7
78.0
44.4
241.0
28.2
391.6
Musculium transversum
Sphaerium stamineum
1.5
5.0
3.5
0.7
3,1
2.4
Oligochaeta (small spp.)
Leeches (small spp.)
Caddis larvae (small spp.)
17.5
29.0 48.0
1.5
0.6
4.9 5.6
0.1
Total
187.7
400.3
* A small number of V. subpurpurea included.
481
4 Collections, 4- to 7-ft. Zone, July 26 — 27, 1915
Lower Lake, Opposite Eagle Packet Landing
Number per square yard
Pounds per acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
Pleurocera sp.
18.5
27.5
153.0
60.5
46.5
55.5
33.0
446.3
302.0
55.8
Amnicola emarginata
Valvata spp.
Musculium transversum
Sphaeriufh stamineum
Pisidium species
17.5
53.0
37.0 167.5
20.0
40.0
0.9
26.5
25.9 55.5
0.8
1.4
Leeches (small spp.)
Asellus sp.
Hyalella knickerbockeri
22.5
52.5
15.0
15.0
3.8
5.8
1.4
0.6
Total
373.0
507.6
1 Collection, 1- to 3-ft. Zone, July 28, 1915
Lower Lake, Opposite Eagle Packet Landing
Number
per square yard
Pounds per
acre
Vivipara contectoides
Pleurocera sp.
30
20
50
150.0
24.0
174.0
Planorbis trivolvis
Pisidium sp.
Valvata spp.
10
30
30
70
7.0
1.2
1.6
9.8
Hyalella knickerbockeri
Leeches (small spp.)
100
20
120
4.0
3.4
7.4
Total
240
191.2
482
2. Foot of Peoria Lake (Wesley) to Pekin
4 Channel Collections, July 2*2 and Aug. 19, 1915
Wesley to Pekin
Number per square yard
Pounds per
acre
Campeloma subsolidum
Lioplax subcarinatum
Vivipara subpurpurea
Pieurocera sp.
49.0
15.0
8.2
15.5
87.7
147.0
18.0
41.0
18.6
224.6
Musculium transversum
16.7
16.7
8.3
8.3
Leeches (small spp.)
Chironomid larvae (small spp.)
Hydropsyche sp. (larva)
61.5
50.0
17.5
129.0
10.4
7.0
3.5
20.9
Total
233.4
253.8
4 Collections, 4- to 7-ft. Zone, Aug. 19, 1915
Wesley to Pekin
Number per square yard
Pound's per
acre
Campeloma subsolidum
Vivipara subpurpurea
Pieurocera species
10.5
4.5
5.0
20.0
31.5
22.5
6.0
60.0
Musculium transversum
Sphaerium stamineum
270.0
2.5
272.5
135.0
1.7
136.7
Leeches (small spp.)
Hydropsyche sp. (larva)
55.0
1.5
56.5
9.3
0.3
9.6
Total
349.0
206.3
483
3. Pekin to Copperas Creek Dam
14 Channel Collections, July 22, 23, 28, and Aug. 19, 1915
Pekin to Copperas Creek Dam
Number per square yard
Pounds per acre
Campeloma subsoliduhi
Lioplax subcarinatus
Vivipara subpurpurea
Pleurocera sp.
17.1
2.6
2.1
7.0
28.8
51.3
3.1
10.5
8.4
73.3
Musculium transversum
Young Unionidae
126.7
0.2
126.9
63.3
0.4
63.7
Leeches (small spp.)
Chironomid larvae (small spp.)
Hydropsyche sp. (larva)
42.0
6.4
1.4
49.8
7.1
0.8
0.2
8.1
Total
205.5
145.1
9 Collections, 4- to 7-ft. Zone, July 22, 23, and Aug. 19, 1915
Pekin to Copperas Creek Dam
Number per square yard
Pounds per
acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
Pleurocera sp.
95.3
8.8
66.7
6.8
177.6
285.9
10.5
333.5
8.1
638.0
Musculium transversum
Young Unionidae
Planorbis trivolvis
102.6
0.1
1.3
104.0
51.3
0.2
0.9
52.4
Leeches (small spp.)
Chironomid larvae (small spp.)
Caddis larvae (small spp.)
23.8
4.0
6.6
34.4
4.0
0.5
0.6
5.1
Total
316.0
695.5
484
7 Collections, 1- to 3-ft. Zone, July 22, 23, 1915
Pekin to Copperas Creek Dam
Number per
square yard
Pounds per
acre
Campeloma subsolidum
92.8
278.4
-
Lioplax subcarinatus
5.7 ,
6.8
108.4
292.4
Vivipara contectoides
1.4
7.0
Pleurocera sp.
8.5
10.2
Musculium transversum
135.7
135.7,
67.8
67.8
Leeches (large sp)
5.7
11.4
Leeches (small spp.)
52.8
8.9
Small oligochaetes
8.5
0.2
Asellus sp.
17.1
116.8
1.6
31.2
Chironomid larvae (large spp.)
8.5
5.6
Chironomid larvae (small spp.)
15.7
2.1
Hydropsyche sp. (larva)
7.1
1.4
Young crayfishes
1.4
Not valued
Total
360.9
391.4
4. Copperas Creek Dam to Havana
8 Channel Collections, Aug. 3, 19, 1915
Copperas Creek Dam to one Mile above Liverpool
Number per square yard
Pounds per
acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
Vivipara subpurpurea
Pleurocera sp.
161.7
17.7
63.8
6.5
13.7
263.4
485.1
21.2
319.0
32.5
16.4
874.2
Musculium transversum
0.3
0.3
0.1
0.1
Leeches (small spp.)
Asellus sp.
Chironomid larvae (small spp.)
18.6
7.2
2.5
28.3
3.1*
0.6
0.3
4.0
Total
292.
878.3
485
4 Collections, 4- to 7-ft. Zone, Aug. 19, 1915
Copperas Creek Dam to one Mile above Liverpool
Number per square yard
Pounds per
acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
Vivipara subpurpurea
Pleurocera sp.
160.5
60.7
50.0
2.0
29.0
302.2
446.7
72.8
250.0
10.0
34.8
814.3
Musculium transversum
1212.5
1212.5
606.2
606.2
Leeches (small spp.)
Chironomid larvae (small spp.)
76.0
20.7
96.7
12.9
2.8
15.7
Total
1611.4
1436.2
8 Channel Collections, July 31 and Aug. 3, 4, 1915
One Mile above Liverpool to Havana
Number per square yard
Pounds per
acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides*
Pleurocera sp.
280.0
74.7
815.6
123.7
1294.0
840.0
89.6
4078.0
148.4
5156.0
Amnicola emarginata
3.0
3.0
0.1
0.1
Leeches (small spp.)
Asellus sp.
Hexagenia bilineata (nymph)
106.7
64.5
0.6
171.8
18.1
6.1
0.5
24.7
Total
1468.8
5180.8
* Including' a few V. subpurpurea.
486
13 Collections, 4- to 7-ft. Zone, July 31 and Aug. 4, 1915
One Mile above Liverpool to Havana
Number per
square yard
Pounds per
acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
Pleurocera sp.
48.8
41.9
22.8
7.3
120.8
164.4
50.2
114.0
8.7
319.3
Planorbis trivolvis
Musculium transversum
Sphaerium stamineum
0.4
3496.9
40.0
3537.3
0.2
1748.5
28.0
1776.7
Leeches (small spp.)
Asellus sp.
I-Iyalella knickerbockeri
131.6
38.9
1.5
172.0
22.3
3.7
trace
26.0
Total
3830.1
2122.0
6 Collections, 1- to 3-ft. Zone, July 31 and Aug. 4, 1915
One Mile above Liverpool to Havana
Number per square yard
Pounds per acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
Pleurocera sp.
90.3
19.0
118.0
3.3
230.6
270.9
22.8
590.0
3.9
887.6
Planorbis trivolvis
10.6
7.4
Musculium
transversum
26.3
38.5
13.1
21.6
Sphaerium
stamineum
1.6
1.1
Oligochaeta
(small
spp.)
6.6
0.2
Leeches (small spp
• )
36.1
6.1
81.0
10.5
Asellus sp.
25.0
2.4
Chironomid
larvae
(small spp.)
13.3
1.8
Total
350.1
919.7
487
5. Havana to Lagrange Dam, 1915
16 Channel Collections, Aug. 2, 4, 5, 6, 27, 1915
Havana to Lagrange Dam (42.5 Miles)
Number per square yard
Pounds per acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides and subpur-
purea
Pleurocera sp.
5.0
0.33
5.57
0.12
0.12
15.0
0.3
16.0
0.6
0.1
Musculium transversum
6.0 6.0
3.0 3.0
Small oligochaetes
Small leeches
Asellus sp.
Hydropsyche larvae
Hexagenia bilineata (nymph)
Chironomid larvae (small spp.)
0.33
1.0
1.0
3.77
1.2
0.12
0.12
0.1
1.7
trace
3.0
0.2
1.0
trace
Total
15.34
22.0
488
22 Collections, 4- to 7-ft. Zone, Aug. 2, 5, 6, 27, 1915
Havana to Lagrange Dam (42.5 Miles)
Number per square yard
Pounds per acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides or subpur-
purea
Pleurocera sp.
48
8
16
1
73
144.0
9.6
80.0
1.2
234.8
Amnicola emarginata
Musculium transversum
4
84
88
0.1
42.0
42.1
Small oligochaetes
9
0.3
Small leeches
8
1.3
Asellus sp.
1.5
31.1
0.1
5.7
Hydropsyche larvae
7.6
1.5
Hexagenia, etc. (nymphs)
2.5
2.2
Chironomid larvae (small spp.)
2.5
0.3
Total
192.1
.
282.6
20 Collections, 1- to 3-ft. Zone, Aug. 2, 5, 6, 1915
Havana to Lagrange Dam (42.5 Miles)
Number per square yard
Pounds per acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides or subpur-
purea
Pleurocera sp.
32.0
2.3
99.3
55.0
10.0
96.0
2.7
385.7
275.0
12.0
Amnicola sp.
Musculium transversum
2.0
91.0
89.0
0.1
44.6
44.5
Small oligochaetes
Small leeches
Asellus sp.
Hydropsyche larvae
Hexagenia, etc. (nymphs)
Chironomid larvae (small spp.)
trace
5.5
trace
4.0 18.3
3.0
5.8
0.9
0.8 5.2
2.7
0.8
Total
208.6
435.5
489
2 Channel Collections, Aug. 6, 1915
Foot of Grand Island to Browning
(9-mile section of narrow, deep channel)
Number per square yard
Pounds per
acre
Campeloma subsolidum
Pleurocera sp.
0.5
1.0
1.5
1.5
1.2
2.7
Musculium transversum •
5.0
5.0
2.5
2.5
Chironomid larvae (small spp.)
Hydropsyche larvae
1.0
5.0
6.0
trace
1.0
1.0
Total
12.5
6.2
10 Collections, 4- to 7-ft. Zone, Aug. 6, 1915
Foot of Geand Island to Browning
(9-mile section of narrow, deep channel)
Number per square yard
Pounds per acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
Vivipara subpurpurea
Pleurocera sp.
71.7
1.6
14.9
3.0
1.2
92.4
215.1
1.9
74.5
15.0
1.4
307.9
Musculium transversum
106.4
106.4
53.2
53.2
Chironomid larvae (small spp.)
Hydropsyche larvae
Hexagenia, etc. (nymphs)
Leeches (small spp.)
1.9
0.5
4.0
3.9
10.3
0.2
0.1
3.6
0.6
4.5
Total
209.1
365.6
490
4 Collections, 1- to 3-ft. Zone, Aug. 6, 1915
Foot of Grand Island to Browning
(9-mile section of narrow, deep channel)
Number per square yard
Pounds per acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
Pleurocera sp.
46.2
2.5
272.5
6.2
327.4
138.6
7.5
1362.5
7.4
1516.0
Musculium transversum
186.2
186.2
93.1
93.1
Hydropsyche larvae
Chironomid larvae (small spp.)
Leeches (small spp.)
3.7
3.7
18.7
26.1
0.7
0.5
3.1
4.3
Total
539.7
1613.4
6. Lagrange Dam to Grafton
14 Collections (averaged), Aug. 11, 1915
Lagrange Dam to Florence
Number per square yard
Pounds per acre
Four channel collections
0.25
trace
Two collections, 4- to 7- ft. zone
Musculium transversum
115.
57.5
Eight collections, 1- to 3-ft. zone
Musculium transversum
Young Unionidae
Small oligochaetes
Hexagenia, etc. (nymphs)
15.6
16.3
0.7
1.2
2.2
1.0
7.8
9.2
1.4
trace
0.9
0.9
Total
18.5
10.1
491
5 Channel Collections, Aug. 10, 1915
Valley City to Kampsville
Number per
square yard
Pounds per
acre
Vivipara subpurpui*ea
1.0
1.0
5.0
5.0
Musculium transversum
Young Unionidae
1.4
0.4
1.8
0.7
0.8
1.5
Small oligochaetes
Planarians
Hydropsyche larvae
Hexagenia, etc. (nymphs)
Chironomid larvae (small spp.)
Perlid nymphs
Gomphid nymphs
6.2
2.0
19.0
0.8
0.2
0.2
0.4
28.8
0.2
trace
3.8
0.7
trace
0.2
1.0
5.9
Total
31.6
12.4
17 Collections, 4- to 7-ft. Zone, Aug. 10, 1915
Valley City to Kampsville
Number per square yard
Pounds per
acre
Campeloma subsolidum
0.2
0.2
0.6
0.6
Musculium transversum
Young Unionidae
12.6
2.0
14.6
6.3
4.0
10.3
Small Oligochaeta
Small leeches
Planarians
Hydropsyche larvae
Hexagenia, etc. (nymphs)
Chironomid larvae (small spp.)
Gomphid nymphs
4.5
0.5
1.0
7.6
3.1
1.8
0.5
19.0
0.1
trace
trace
1.5
0.2
1.2
5.7
Total
33.8
16.6
492
Collections, 1- to 3-ft. Zone, Aug. 10, 1915
Valley City to Kampsville
♦
■Number per square yard
Pounds per
acre
Musculium transversum
4.8
4.8
2.4
2.4
Oligochaetes, small
Hydropsyclie larvae
Hexagenia, etc. (nymphs)
Chironomid larvae (small spp.)
3.0
2.2
5.0
1.2
11.4
0.1
0.4
4.5
0.1
5.1
Total
16.2
7.5
7 Channel Collections, Aug. 12, 22, 23, 1915
Head of Diamond Island to Grafton
Number per square yard
Pounds per acre
Musculium transversum
Young Unionidae
2.0
2.8
0.8
1.0
2.6
1.6
Chironomid larvae (small spp.)
Hexagenia, etc. (nymphs)
Hydropsyche larvae
Gomphid nymphs
Oligochaetes (small spp.)
0.4
3.0
0.5 25.5
0.2
21.4
trace
2.7
0.1 3.9
0.4
0.7
Total
28.3
6.5
493
12 Collections, 4- to 7-ft. Zone, Aug. 12, 22, 23, 1915
Head of Diamond Island to Grafton
Number per square yard
Pounds per acre
Musculium transversum
Young Unionidae
4.4
5.7
1.3
2.2
4.8
2.6
Chironomid larvae (small spp.)
Corethra larvae
Hexagenia, etc. (nymphs)
Hydropsyche larvae
Gomphid nymphs
Oligochaetes (small spp.)
1.4
0.5
5.5
11.3
0.9
0.1
2.9
0.2
trace
4.9
5.5
0.2
0.1
0.1
Total
17.0
10.3
12 Collections, 1- to 3-ft. Zone, Aug. 12, 22, 23, 1915
Head of Diamond Island to Grafton
Number per square yard
Pounds per
acre
Campeloma subsolidum
0.1
0.1
0.3
0.3
Musculium transversum
Young Unionidae
6.3
1.6
7.9
3.1
3.2
6.3
Chironomid larvae (small spp.)
Corethra larvae
Hexagenia, etc. (nymphs)
Caddis larvae ("stick")
Gomphid nymphs
Oligochaetes (small spp.)
Leeches (small spp.)
1.6
0.7
23.2
0.1
0.1
3.2
0.4
29.3
0.2
trace
20.8
trace
0.2
0.1
trace
21.3
Total
37.3
27.9
494
II. Bottom Fauna of the Lakes of the Illinois Valley, Copperas
Creek Dam to Lagrange, 1914 — 1915
1. Deeper, Bottom-Land Type (Clear-Mud, Liverpool,
Thompson, Dogfish, Sangamon Bay)
Clear Lake, Sept. 1, 1915. Bottom Fauna
8 Collections, Depth, 8 to 8.5 ft. No Vegetation
Number per square yard
Pounds per
acre
C'ampeloma subsolidum
Vivipara contectoides
1.2
2.7
3.9
3.6
13.5
17.1
Musculium transversum
Pisidium sp.
371.8
33.1
404.9
185.5
1.3
186.8
Leeches (small spp.)
Chironomid larvae (large spp.)
Small Oligochaeta
16.0
13.0
8.7
37.7
2.7
8.7
0.3
11.7
Total
446.5
215.6
Clear-Mud Lake, Sept. 1, 1915. Bottom Fauna
12 Collections, Depth, 1 to 6 ft.
(Some vegetation at two shallow stations)
Number per
square yard
Pounds per
acre
Campeloma subsolidum
Vivipara contectoides
8.4
19.3
27.7
25.2
96.5
121.7
Musculium transversum
Pisidum sp.
Musculium jayanum
219.1
30.0
0.1
249.2
109.5
1.2
trace
110.7
Leeches (small spp.)
Chironomid larvae (large spp.)
Chironomid larvae (small spp.)
42.1
15.8
0.8
58.7
7.1
10.5
0.1
17.7
Total
335.6
250.1
495
Liverpool Lake, Sept. 1, 1915. Bottom Fauna
6 Collections, Depth, 6.5 to 9.5 ft. No Vegetation
Number per
square yard
Pounds per
acre
Campeloma subsolidum
Vivipara contectoides
2.6
3.3
5.9
7.8
16.5
24.3
Musculium transversum
Pisidium sp.
Valvata spp.
191.6
29.1
1.6
222.3
95.5
1.1
0.1
96.7
Leeches (small spp.)
Chironomid larvae (large
spp.)
20.6
26.6
47.2
3.4
17.8
21.2
Total
275.4
142.2
Liverpool Lake, Sept. 1, 1915. Bottom Fauna
9 Collections, Depth 1.5 to 6 ft.
(Some vegetation at shallower stations)
Number per square yard
Pounds per
acre
Vivipara contectoides
23.4
23.4
117.0
117.0
Musculium transversum
Pisidium sp.
Valvata spp.
Amnicola limosa
A. emarginata
6.6
10.0
2.2
5.5
2.2
26.5
3.3
0.4
0.1
0.3
0.1
4.2
Leeches (small spp.)
Chironomid larvae (large spp.)
15.5
38.2
53.7
2.6
25.6
28.2
Total
103.6
149.4
496
Thompson Lake, Aug. 12 — 20, 1914. Bottom Fauna
8 Collections,* Depth, 7 to 9 ft.
(No vegetation;, all mud bottom)
Number per square yard
Pounds per acre
Campeloma subsolidum
Lioplax subcarinatus
21.3
. 10.5 31.8
63.9 '
12.6 76.5
Valvata spp.
Musculium transversum
Pisidium sp.
470.6
208.3 936.1
257.2
25.8
104.0 140.0
10.2
Small Oligochaeta
Small leeches
Chironomid larvae (large spp.)
Chironomid larvae (small spp.)
Palpomyia larvae
Caddis larvae >
4.0
23.5
123.7
212.0
46.7
3.1
11.0
0.1
3.9
82.4
94.2
6.5
0.2
1.1
Total
1179.9
310.7
* All above "cut-road."
Thompson Lake, Aug. 12 — 20, 1914. Bottom Fauna
10 Collections,* Depth, 1 to 6 ft. No Vegetation
(Eight collections, mud bottom; two collections, sandy)
Number per
square yard
Pounds per
acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
83.0
63.0
72.5
218.5
249.0
75.6 ■
362.5
687.1
Amnicola limosa
A. emarginata
Valvata spp.
Musculium transversum
Pisidium sp.
40.0
31.0
362.0
79.0
442.5
954.5
2.2
1.1
19.9
. 39.5
17.6
80.3
Small Oligochaeta
Small leeches
Chironomid larvae (large spp.)
Caddis larvae
10.0
72.0
180.0
33.0
295.0
0.3
12.2
120.0
3.3
135.8
Total
1468
903.2
All north of "cut-road."
497
Thompson Lake, Aug. 12 — 20, 1914. Bottom Fauna
12 Collections,* Depth, 1 to 6 ft. All in Vegetation
(Eleven collections, mud bottom; one collection, sandy)
Number per square yard
Pounds per
acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
28.7
2.0
38.3
69.0
86.1
2.4
191.5
280.0
Amnicola limosa
Valvata spp.
Musculium transversum
Pisidium sp.
0.8
69.5
65.4
35.8
171.5
trace
3.8
32.7
1.4
37.9
Small leeches
9.5
1.6
Planarians
2.5
trace
Chironomid larvae (large spp.)
268.0
311.2
179.5
183.5
Chironomid larvae (small spp.)
2.5
€.3
Caddis larvae
17.5
1.7
Caenis nymphs
0.8
trace
Hyalella knickerbockeri
10.4
0.4
Total
551.7
501.4
All north of "cut-road."
Thompson Lake,* Aug 12 — 20, 1914. Bottom Fauna
4 Collections, Depth, 2 to 4 ft. All in Vegetation
Number
per square
yard
Pounds per acre
Chironomid larvae (large spp.)
Small oligochaetes
330
30
221.1
1.1
Total
360
222.2
* Foot of lake, below "cut-road."
498
Thompson Lake, Aug. 12 — 20, 1914. Bottom Fauna
3 Sand-Bottom Collections,* Depth, 1 to 5 ft.
(Some vegetation)
Number per
square yard
Pounds per
acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
46.6
23.3
51.6
121.5
139.8
27.9
258.0
425.7
Valvata spp.
Musculium transversum
Pisidium sp.
96.6
55.0
150.0
301.6
5.3
27.5
6.0
38.8
Chironomid larvae (large spp.)
Small leeches
Caddis larvae
Caenis nymphs
Large libellulid (nymphs)
Hyalella knickerbockeri
10.0
18.3
26.6
3.3
3.3
41.6
103.1
6.7
3.1
2.6
0.2
8.2
1.6
22.4
Total
526.2
486.9
* All above cut-road. These three collections, arranged separately here, are
also included in tables preceding-.
Thompson Lake, Aug. 28, 1915. Bottom Fauna
5 Collections,* Depth, 7 to 9 ft. No Vegetation
Number per square yard
Pounds per acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
23.0
11.2
66.3
100.5
69.0
13.4
331.5
413.9
Valvata spp.
54.7
3.0
Musculium transversum
106.5
53.2
372.7
64.6
M. jayanum
trace
Pisidium sp.
211.5
8.4
Small leeches
27.0
4.5
Small Oligochaeta
1.2
48.7
trace
18.1
Chironomid larvae
(large
spp.)
20.3
13.6
Caddis larvae
0.2
trace
Total
521.9
496.6
* All above "cut-road.
499
Thompson Lake, Aug. 28, 1915. Bottom Fauna
7 Collections,* Depth, 1 to 6 ft.
(No vegetation; all mud bottom)
Number per
square yard
Pounds per
acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
32.7
19.5
97.8
150.0
98.1
23.4
489.0
610.5
Valvata spp.
Musculium transversum
M. jayanum
Pisidium sp.
43.5
30.2
trace
188.1
261.8
2.3
15.1
7.5
24.9
Small leeches
Chironomid larvae (large spp.)
19.5
32.9
13.4
3.3
12.2
8.9
Total
444.7
647.6
All above "cut-road."
Thompson Lake, Aug. 28, 1915. Bottom Fauna
7 Collections,* Depth, 1 to 6 ft. All in Vegetation
(Three collections, mud bottom; four collections, sand and mud)
Number per square yard Pounds per acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
117.0
11.4
137.0
265.4
Amnicola limosa
42.8
2.3
Valvata spp.
109.2
6.0
Musculium transversum
11.5
240.6
5.7
17.0
Musculium jayanum
trace
Pisidium
77.1
3.0
Chironomid larvae (large spp.)
11.7
7.8
Caddis larvae
2.1
55.7
0.2
14.5
Small leeches
37.7
6.4
Planarians
4.2
0.1
Total
372.3
296.9
* All above "cut-road."
500
Thompson Lake,* Aug. 28,. 1915. Bottom Fauna
5 Collections, Depth, 2 to 6 ft. All in Vegetation
.
Number per square yard
Pounds per acre
Vivipara contectoides
157
785.0
Pisidium sp.
12
0.4
Small leeches
169
28.7
Total
338
814.1
* Foot of lake, below "cut-road."
Thompson Lake, Aug. 28, 1915. Bottom Fauna
4 Sand-and-mud Bottom Collections,* Depth, 1 to 6 ft.
(All in vegetation)
•
Number per square yard
Pounds per acre
Campeloma subsolidum
Vivipara contectoides
Lioplax subcarinatus
31.5
54.0 96.2
10.7
94.5
270.0 377.3
12.8
Valvata spp.
Amnicola limosa
Musculium transversum
Pisidium sp.
118.7
50.0
243.9
5.2
70.0
6.5
2.7
14.6
2.6
2.8
Small leeches
57.5
9.7
Planarians
7.5
83.2
0.2
19.9
Chironomid larvae (large spp.)
14.5
9.7
Caddis larvae
3.7
0.3
Total
423.3
411.8
* All above "cut-road." These four collections, averaged separately here,
are also included in a preceding table.
501
Dogfish Lake, Aug. 18, 1914. Bottom Fauna
3 Collections, Depth, 6.5 to 7 ft. No Vegetation
Number per square yard
Pounds per
acre
Vivipara contectoides
1.6
1.6
8.0
8.0
Musculium transversum
Pisidium sp.
Valvata spp.
3.3
33.3
5.0
41.6
1.6
1.3
0.2
3.1
Leeches (small spp.)
Chironomid larvae (large spp.)
16.6
170.0
186.6
0.9
11.4
12.3
Total
229.8
23.4
Dogfish Lake, Aug. 18, 1914. Bottom Fauna
5 Collections, Depth, 2 to 6 ft. All in Vegetation
Number per
square yard
Pounds per
acre
Vivipara contectoides
Campeloma subsolidum
66.0
2.0
68.0
330.0
6.0
336.0
Musculium transversum
Pisidium sp.
Valvata spp.
Amnicola limosa
Planorbis, small sp.
10.0
128.0
160.0
2.0
2.0
302.0
5.0
5.1
8.8
0.1
0.1
19.1
Leeches (small spp.)
Chironomid larvae (large
Chironomid larvae (small
Small libellulid nymphs
Caddis larvae
spp.)
spp.)
12.0
40.0
20.0
2.0
8.0
82.0
2.0
26.8
2.8
10.0
0.8
42.4
Total
452.0
397.5
502
Dogfish Lake, Aug. 31, 1915. Bottom Fauna
12 Collections, DErTH, 7.5 to 8.5 ft. No Vegetation
Number per square yard
Pounds per
acre
Vivipara contectoides
Lioplax subcarinatus
Campeloma subsolidum
10.6
5.0
2.7
18.3
53.0
6.0
8.1
67.1
Musculium transversum
Pisidium sp.
Valvata spp.
Amnicola emarginata
Planorbis (small sp.)
Physa (small sp.)
10.5
74.5
165.3
37.5
1.6
1.1
290.5
5.2
2.9
9.0
1.3
0.1
trace
18.5
Leeches (small spp.)
38.8
6.5
Chironomid larvae (large spp.)
88.0
155.0
58.9
66.4
Small Oligochaeta
11.6
0.4
Hyalella knickerbockeri
16.6
0.6
Total
463.8
152.0
Dogfish Lake, Aug. 31, 1915. Bottom Fauna
3 Collections, Depth, 1 to 6 ft. Very Little Vegetation
Number per square yard
Pounds per
acre
Pisidium sp.
Valvata spp.
Amnicola emarginata
33.3
66.6
66.6
166.5
1.3
3.6
2.4
7.3
Leeches (small spp.)
Chironomid larvae (large spp.)
Small Oligochaeta
50.0
176.6
16.6
243.2
8.5
117.9
0.5
126.9
Total
409.7
134.2
503
Sangamon Bay, Sept. 8, 1915. Bottom Fauna
Collections, Depth, 6.5 to 7.5 ft. No Vegetation
Number per square yard
Pounds per
acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
9.1
13.7
1.5
24.3
27.3
16.4
7.5
51.2
Musculium transversum
Valvata spp.
81.8
9.2
91.0
40.9
0.5
41.4
Leeches (small spp.)
Chironomid larvae (large spp.)
Caddis larvae
Hexagenia nymphs
16.3
15.6
5.6
0.5
38.0
2.7
10.4
0.5
0.4
14.0
Total
153.3
106.6
Sangamon Bay, Sept. 8, 1915. Bottom Fauna
4 Collections, Depth, 1.5 to 6 ft. No Vegetation
Number per square yard
Pounds per acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
Pleurocera sp.
35.7
12.7
4.0
2.5
54.9
107.1
15.2
20.0
3.0
145.3
Musculium transversum
Valvata spp.
217.5
15.0
232.5
108.7
0.8
109.5
Leeches (small)
Chironomid larvae XlarSe spp.)
Palpomyia larvae
Caddis larvae
Hexagenia, etc. (nymphs)
27.0
3.7
0.7
11.5
2.5
45.4
4.5
2.4
trace
1.1
2.2
10.2
Total
332.8
265.0
504
2. Deep, Sand-Beach Type (Quiver, Matanzas)
Quiver Lake, Sept. 30 to October 12, 1914. Bottom Fauna
15 Collections, Depth:, 7 to 12 ft. No Vegetation
Number per square yard
Pounds per acre
Campeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
Vivipara subpurpurea
Pleurocera sp.
58.2
48.0
462.0
trace
177.3
745.5
174.6
57.6
2,310.0
212.4
2,754.6
Amnicola emarginata
Musculium jayanum
Pisidium sp.
Young Unionidae
1.3
3.3
1.0
0.6
6.2
1.7
trace
1.2
2.9
Chironomid larvae.
Small leeches
Large leeches
Small Oligochaeta
Caddis larvae
Agrionid nymph
Asellus sp.
(small spp.)
24.0
52.6
10.0
54.0
2.6
0.6
11.3
161.1
3.3
8.9
32.0
1.8
0.2
0.3
1.0
47.5
Total
912.8
2,805.0
505
Quivek Lake, Sept. 30 to October 12, 1914. Bottom Fauna
17 Collections, Depth, 1 to 6 ft.
(Most in vegetation)
Number per
square yard
Pounds per
acre
C'ampeloma subsolidum
24.7
74.1
Lioplax subcarinatus
11.1
85.1
13.3
329.7
Vivipara contectoid'es
48.2
241.0
Pleurocera sp.
1.1
1.3
Amnicola emarginata
42.3
1.5
Amnicola limosa
8.2
0.4
Valvata spp.
9.4.
0.5
Physa, small
7.6
124.0
1.7
33.4
Young Unionidae
6.3
12.6
Musculium transversum
32.0
16.0
Pisidium sp.
.18.2
0.7
Chironomid larvae, large red
Chironomid larvae, small
Palpomyia larvae
Caddis larvae
Hexagenia nymph
Agrionid nymph
Large libellulid nymph
Small leeches
Large leeches
Small Oligochaeta
Hyalella knickerbockeri
1.1
4.4
0.3
trace
0.4
0.5
4.0
5.7
7.0
0.4
1.4
25.2
Total
38.8.3
Quiver Lake, Aug. 30, 1915. Bottom Fauna
3 Collections,* Depth, 7 to 10 ft. No Vegetation
Number per square yard
Pounds per
acre
Vivipara contectoides
160
160
800
800
Small leeches
Caddis larvae
Asellus sp.
8.6
6.0
11.6
26.2
1.4
0.6
1.1
3.1
Total
186 2
S03.1
All opposite Bishop's.
506
Quiver Lake, Aug. 30, 1915. Bottom Fauna
14 Collections, Depth, 1 to 6 ft. Most with Vegetation
Number per square yard
Pounds per
acre
Vivipara contectoid'es
7.1
7.1
35.5
35.5
Amnicola limosa
Musculium transversum
16.0
1.0
17.0
8.8
0.5
9.3
Small leeches
Chironomid larvae (large
Chironomid larvae (small
Agrionid nymph
spp.)
spp.)
11.9
162.8
13.5
2.1
-190.3
2.0
109.0
1.9
1.0
113.9
Total
214.4
158.7
Matanzas Lake, Sept. 4, 1915. Bottom Fauna
9 Collections, Depth, 6.5 to 8.5 ft. No Vegetation
Number per square yard
Pounds per acre
Musculium transversum
Pisidium sp.
Valvata spp.
63.3
206.6 284.3
14.4
31.6
8.2 40.6
0.8
Small Oligochaeta
Small leeches
Chironomid larvae (large spp.)
Palpomyia larvae
4.4
30.7
58.4
18.6
4.7
0.1
5.2
18.0
12.4
0.3
Total
342.7
58.6
507
Matanzas Lake, Sept. 4, 1915. Bottom Fauna
6 Collections (in Ceratophyllum and Potamogeton), Depth 2 to 6 ft.
(Some vegetation at all stations)
Number per square yard
Pounds per
acre
Campeloma subsolidum
Pleurocera sp.
Vivipara contectoides
5.0
1.6
8.3
14.9
15.0
1.9
41.5
58.4
Musculium transversum
Pisidium sp.
Valvata spp.
15.0
48.3
3.3
66.6
7.5
1.9
0.2
9.G
Leech, small
Chironomid larvae (large spp.)
Hexagenia, etc. (nymphs)
Caenis nymph
13.8
2.3
6.6
3.3
26.0
2.3
1.5
5.9
0.2
9.9
Total
107.5
77.9
3. Shallower, Weedy Type (Flag, Seees, Stewart)
Flag Lake, Oct. 6, 1914. Bottom Fauna
3 Collections, Depth, 4 to 5 ft. All in Vegetation
Number per
square yard
Pounds per
acre
Musculium transversum
Pisidium sp.
Valvata spp.
Amnicola limosa
Physa, small sp.
6.6
93.3
276.6
20.0
46.6
443.1
3.3
3.7
15.1
1.1
2.5
25.7
Leech, small sp.
Chironomid larvae
Chironomid larvae
Agrionid nymph
Caddis larvae
(large spp.)
(small spp.)
33.3
33.3
110.0
3.3
6.6
186.5
5.6
22.1
15.4
1.5
0.6
45.2
Total
629.6
70.9
508
Flag Lake, Aug. 27 — 30, 1915. Bottom Fauna
15 Collections, Depth, 3.5 to 5 ft. Little Living Vegetation
Number per square yard
Pounds per
acre
Vivipara contectoides
1.0
1.0
5.0
5.0
Leech, small
Chironomid larvae (large spp.)
Chironomid larvae (small spp.)
37.8
23.3
8.4
69.5
•
6.4
15.4
1.1
22.9
Total
70.5
27.9
Seebs Lake, Oct. 13, 1914. Bottom Fauna
7 Collections, Depth, 2.5 to 5 ft. Some Vegetation
Number per square yard
Pounds per
acre
Vivipara contectoides
2.8 2.8
14.0
14.0
Musculium transversum
Pisidium sp.
Valvata spp.
Amnicola limosa
Amnicola emarginata
Physa, small sp.
8.5
57.1
130.0
233.0
27.5
5.7
4.2
4.2
2.3
7.1
1.5
0.3
0.1
15.5
Leeches (small spp.)
Leeches (large spp.)
Chironomid larvae (large spp.)
Small Oligochaeta
Libellulid nymph (small sp.)
Hyalella knickerbockeri
8.5
18.5
48.5
480.0 702.5
4.2
142.8
1.4
36.0
32.5
16.8 94.5
2.1
5.7
Total
938.3
124.0
509
Seebs Lake, Sept. 4, 1915. Bottom Fauna
Collections, Depth, 2 to 5.5 ft. Little Vegetation
Number per
square yard
Pounds per
acre
Vivipara contectoides
3.7
3.7
18.5
18.5
Valvata spp.
34.0
34.0
1.8
1.8
Leeches (small spp.)
Chironomid larvae (large spp.)
24.2
2.3
26.5
4.1
1.5
5.6
Total
64.2
25.9
Stewaet Lake, Sept. 7, 1915. Bottom Fauna
12 Collections, Depth, 2 to 5.5 ft. All in Vegetation
Number per square yard Pounds per acre
Campeloma subsolidum
8.7
26.1
Lioplax subcarinatus
12.0
20.8
14.4
41.0
Vivipara contectoides
0.1
0.5
Musculium transversum
21.0
10.5
Musculium jayanum
3.5
1.9
Pisidium sp.
7.8
69.8
0.3
24.4
Valvata spp.
32.5
1.7
Young unionid
5.0
10.0
Small Oligochaeta
2.5
0.1
Leeches, small
36.0
6.1
Chironomid larvae (large spp.)
1.6
54.0
1.0
8.4
Chironomid larvae (small spp.)
6.6
0.9
Palpomyia larvae
4.0
0.2
Hyalella knickerbockeri
3.3
0.1
Total
144.6
73.8
510
4. Very Shallow, very Weedy Type (Duck, Dennis, Crane)
Duck — Dennis Lake, Oct. 2, 1914. Bottom Fauna
5 Collections, Depth, 2.5 to 4 ft. All in Vegetation
Number per square yard
Pounds per acre
Valvata spp.
Physa, small sp.
Amnicola limosa
A. emarginata
Pisidium sp.
188.0
6.0
8.0
12.0
2.0
216
Small leeches
Small Oligochaeta
Chironomid larvae (large spp.)
Chironomid larvae (small spp.)
Agrionid nymph
Libellulid nymph
Corixa, small sp.
Hyalella knickerbockeri
2,0
12.0
106.0
72.0
6.0
4.0
12.0
62.0
276
10.3
1.3
0.4
0.4
trace
0.3
0.4
71.0
10.0
3.0
10.0
0.8
2.4
12.4
97.9
Total
492
110.3
Ceane Lake, Sept. 7, 1915. Bottom Fauna
5 Collections, Depth, 1 to 3.5 ft. Some Vegetation
Number per square yard
Pounds per
acre
Campeloma
subsolidum
14.0
14.0
42.0
42.0
Musculium
transversum
28.0
14.0
34.0
14.3
Valvata spp
_
6.0
0.3
Chironomid
larvae
( small
spp.)
6.0
0.8
Leeches (small spp
.)
26.0
4.4
Chironomid
larvae
(large
spp.)
4.0
78.0
2.6
22.7
Palpomyia
arvae
16.0
1.1
Hexagenia,
etc. (n-
ymphs)
14.0
12.6
Caddis larvae
12.0
1.2
Total
126.0
79.0
511
5. Dead Timber and Brush Areas
Dead Timber and Brush Areas, Vicinity of Havana,* Aug. 18 to Oct. 16, 1914
Bottom Fauna
6 Collections, Depth, 1.5 to 4 ft. Some Vegetation
Number per square yard
Pounds per
acre
Campeloma subsolidum
1.6
6.6
4.8
29.8
Vivipara contectoides
5.0
25.0
Amnicola emarginata
45.0
1.6
A. limosa
10.0
0.5
Valvata spp.
531.6
29.2
Physa, small sp.
6.6
1.5
Planorbis trivolvis
1.6
724.5
1.1
87.1
Planorbis, small sp.
3.3
trace
Young Unionidae
1.6
3.2
Musculium transversum
98.2
49.0
Pisidium sp.
26.6
1.0
Chironomid larvae (large spp.)
Chironomid larvae (small spp.)
Palpomyia larvae
Caddis larvae
Small leeches
Small Oligochaeta
Hyalella knickerbockeri
26.8
8.6
0.7
0.3
2.2
trace
5.4
44.0
Total
1,000.9
160.9
lakes.
Head Quiver Lake; head Dogfish Lake; ridge between Flag and Thompson
Dead Timber and Brush Areas, Vicinity of Havana,* Aug. 31 to Sept. 11, 1915.
Bottom Fauna
10 Collections, Depth, 1.5 to 3.5 ft. Some Vegetation
Number per square yard
Pound's per
acre
Vivipara contectoides
33.5
33.5
167.5
167.5
Valvata spp.
Small Planorbis sp.
Musculium jayanum
13.0
1.0
1.0
15.0
0.7
0.1
0.5
1.3
Chironomid larvae (large
Small leeches
Hyalella knickerbockeri
spp.)
41.0
37.0
present
78.0+
27.4
6.2
33.6+
Total
126.5+
202.4+
* Head of Clear Lake ; head of Dogfish Lake ; ridge between Quiver and Dogfish
lakes ; ridge between Flag and Thompson lakes.
512
III. Weed Fauna, 1- to 4-Foot Zone, Lakes and Backwaters
in Vicinity of Havana, 1914
Dead Timber Ridge between Flag and Thompson Lakes, Oct. 6, 1914,
Opposite "Warner's Cut," in Ceratophyllum and Algae
Weed Fauna, Upper 9 Inches (Depth, 2 ft.)
No. per sq. yard
Pounds per acre
Valvata spp.
Amnicola limosa
Physa (small spp.)
Planorbis trivolvis
22,500
4,500
1,500
750
1,347.5
209.0
2,164.0
82.5
525.0
Chironomid larvae (small spp.)
Pelocoris
Hyalella knickerbockeri
'750
270
3,000
52.5
256.5 429.0
120.0
Total
33,270
2,593.0
Head of Flag Lake, Oct. 7, 1914, in Smartweed and Scirpus
Weed Fauna, Upper 9 Inches (Depth, 1.5 ft.)
No. per sq. yard
Pounds per acre
Physa (small spp.)
Amnicola limosa
Valvata spp.
Planorbis trivolvis
3,750
1,500
150
300
206.2
57.0
481.4
8.2
210.0
Chironomid larvae (small spp.)
Agrionid nymphs
Small libellulid nymphs
Pelocoris femoratus
Hyalella knickerbockeri
4,500
1,500
750
375
6,000
315.0
750.0
375.0 2,036.2
356.2
240.0
Total
18,825
2,517.6
513
Middle of Duck Lake, Oct. 2, 1914, in Potamogeton pectinatus
Weed Fauna, Upper 9 Inches (Depth, 4 ft.)
No. per sq. yard Pounds per acre
Valvata spp.
Amnicola limosa
Planorbis trivolvis
Pliysa (small spp.)
37,500
1,500
375
75
2,062.5
55.5
. 2,421.7
262.5
41.2
Chironomid larvae (small spp.)
Hyalella knickerbockeri
375
1,500
26.2
86.2
60.0
Total
41,325
2,507.9
Foot of Thompson Lake, West Side, Aug. 12, 1914, in Potamogeton pectinatus
Weed Fauna, Upper 9 Inches (Depth, 3.5 ft.)
No. per sq. yard
Pounds per acre
Physa (small spp.)
Planorbis (small spp.)
9,600
120
528.0
534.6
6.6
Caenis nymphs
Agrionid nymphs
Chironomid larvae (small spp.)
Hyalella knickerbockeri
1,920
2,400
6,000
4,500
153.6
1,200.0
1,953.6
420.0
180.0
Total
24,540
2,488.2
514
Foot of Thompson Lake, East Side, Aug. 14, 1914, in Ceratophyllum,
Smartweed, and Algae
Weed Fauna, Upper 9 Inches (Depth, 2.5 ft.)
No. per sq. yard
Pounds
per acre
Physa (small spp.)
6,000
335.0
Planorbis (small spp.)
240
13.2
Planorbis trivolvis
600
420.0
991.4
Valvata spp.
2,400
132.0
Amnicola limosa
2,400
91.2
Pelocoris femoratus
240
228.0
,
Small libellulid nymphs
1,200
600.0
Agrionid nymphs
600
300.0
1,314.0
Caenis sp. (nymphs)
1,200
96.0
Small green chironomid larvae
600
42.0
Hyalella knickerbockeri
1,200
48.0
Total
16,680
2,305.4
Middle of Flag Lake, Oct. 6, 1914, in Potamogeton, Ceratophyllum, and Algae
Weed Fauna, Upper 9 Inches (Depth, 4 ft.)
No. per sq. yard
Pounds per acre
Amnicola limosa
Physa (small spp.)
Valvata spp.
13,125
750
375
498.5
41.2 560.3
20.6
Small libellulid nymphs
Agrionid nymphs
Chironomid larvae (small spp.)
Hyalella knickerbockeri
375
450
750
6,000
187.5
225.0
705.0
52.5
240.0
21,825
1,265.3
515 . -
Foot of Thompson Lake, Middle, Aug. 14, 1914, in Potamogeton pectinatus
Weed Fauna, Upper 9 Inches (Depth, 4.5 ft.)
No. per sq. yard
Pounds per acre
Amnicola limosa
Physa (small spp.)
Valvata spp.
6,000
960
720
228.0
52.8 320.4
39.6
Pelocoris femoratus
Agrionid nymphs
Caenis sp., nymphs
Chironomid larvae (small spp.)
Hyalella knickerbockeri
60
480
480
600
2,400
57.0
240.0
38.4 833.4
402.0
96.0
11,700
1,153.8
IV. Bottom and Weed Fauna, Littoral Zone of Glacial Lakes
of Northeastern Illinois, 1916
1. Bottom Fauna
Deep Lake, August — October, 1916. Bottom Fauna
7 Collections, Littoral Zone, 1 to 7 ft. Some Vegetation
Number per square yard
Pounds per acre
Pisidium spp.
Amnicolidae
Valvatidae
Physa
Planorbis
4.0
13.9
2.9
3.6
15.4
39.8
Leeches, small spp.
12.5
•
2.1
Chironomid larvae (small spp.)
59.6
8.3
Caenis nymphs
3.0
0.2
Hexagenia, etc. (nymphs)
47.0
42.3
Caddis larvae (on Chara)
56.5
5.6
Sand-case caddis larvae
91.0
18.2
510.7
169.0
Libellulid nymphs
22.0
11.0
Agrionid nymphs
28.1
14.0
Gomphid nymphs
12.5
42.5
Pelocoris femorata
19.3
18.3
Hyalella knickerbockeri
156.2
6.2
Asellus sp.
3.0
0.3
Total
1,006.9
208.8
516
Cedar Lake, August — October, 1916. Bottom Fauna
24 Collections, Littoral Zone, 1 to 7 ft. Some Vegetation
Number per square yard
Pounds per
acre
Sphaerium striatinum
4.4
3.0
Musculium transversum
11.0
5.5
Pisidium spp.
24.2
0.9
Amnicolidae
37.4
121.0
2.0
24.2
Valvatidae
22.0
1.2
Physa spp.
11.0
2.5
Planorbis
6.6
0.3
Unionidae, young
4.4
8.8
Oligochaeta (small spp.)
4.4
0.1
Chironomid larvae (small spp.)
46.2
6.4
Palpomyia larvae
1.1
0.1
Polycentropus larvae
trace
Sand-case caddis larvae
26.4
5.2
Caddis larvae (on Chara)
41.8
4.1
Misc. caddis larvae
19.8
1.9
430.1
135.6
Hexagenia, etc. (nymphs)
85.8
77.2
Agrionid .nymphs
17.6
8.8
Libellulid nymphs
15.4
16.5
Gomphid nymphs
2.2
7.4
Beetles, small
11.0
0.7
Hyalella knickerbockeri
143.0
5.7
Asellus sp.
15.4
1.5
Total
159.8
517
Lake Zurich, August — October, 1916. Bottom Fauna
13 Collections, Littoral Zone, 1 to 7 ft. Some Vegetation
Number per square yard
Pounds per acre
Campeloma subsolidum
3.3
3.3
9.9
9.9
Pisidium spp.
Amnicolidae
Valvatidae
21.3
84.5
84.5
190.3
0.8
4.6
4.6
10.0
Oligochaeta (small spp.)
3.3
0.2
Leeches (small spp.)
6.6
1.1
Chironomid larvae (small spp.)
94.6
13.2
Palpomyia larvae
6.6
0.5
Corethra larvae
13.4
0.5
Sand-case caddis larvae
38.7
226.6
7.7
49.2
Polycentropus larvae
1.5
0.3
Agrionid nymphs
1.5
0.7
Sialis larvae
1.5
0.9
Hexagenia, etc. (nymphs)
25.3
22.8
Hyalella knickerbockeri
33.6
1.3
Total
420.2
69.1
Crystal Lake, August — October, 1916.
6 Collections, Littoral Zone, 1 to 7 ft.
Bottom Fauna
Some Vegetation
Number per square yard
Pounds per
acre
Amnicolidae
58.5
3.2
Valvatidae
58.5
168.0
3.2
16.0
Planorbis sp.
47.5
2.6
Unionidae, young
3.5
7.0
Chironomid larvae (small spp.)
3.5
0.5
Ceratopogon larvae
3.5
0.2
Hexagenia, etc. (nymphs)
11.0
9.9
Libellulid nymphs
3.5
1.7
Gomphid nymphs
3.5
340.0
11.9
40.4
Agrionid nymphs
3.5
1.7
Caddis larvae (on Chara)
3.5
0.4
Sand-case caddis
11.0
2.2
Hyalella knickerbockeri
297.0
11.9
Total
508.0
•
56.4
518
Long Lake, August — October, 1916. Bottom Fauna
6 Collections, Littoral Zone, 1 to 7 ft. Some Vegetation
Number per
square yard
Pounds per
acre
Sphaerium sp.
3.5
3.5
1.7
1.7
Chironomid larvae (small spp.)
Hexagenia, etc. (nymphs)
Sand-case caddis larvae
Caddis larvae (on Chara)
Sialis larvae
Gomphid nymphs
Hyalella knickerbockeri
36.5
11.0
80.5
22.0
7.2
3.5
29.3
190.0
5.1
9.9
16.1
2.2
4.3
11.9
1.2
50.7
Total
193.5
52.4
Sand Lake, August — October, 1916. Bottom Fauna
10 Collections, Littoral Zone, 1 to 5 ft. Some Vegetation
Number per square yard
Pounds per
acre
Amnicolidae
Valvatidae
2.2
8.8
11.0
0.1
0.5
0.6
Oligochaeta (small spp.)
Chironomid larvae (small spp.)
Sand-case caddis larvae
Agrionid nymphs
Gomphid nymphs
2.2
' 13.2
13.2
2.2
2.2
33.0
0.1
1.8
2.6
1.1
7.5
13.1
Total
44.0
13.7
519
Pistakee Lake, August — October, 1916. Bottom Fauna
29 Collections, Littoral Zone, 1 to 7 ft. Some Vegetation
Number per square yard
Pound's per acre
Goniobasis sp.
18.0
18.0
10.82 10.82
Sphaerium sp.
Pisidium sp.
Amnicolidae
Valvatidae
Physa spp.
Planorbis spp.
Unionidae, young
5.9
53.7
260.9
38.5
4.4
0.6
2.2
366.2
2.9
2.1
14.3
2.1
0.2
trace
4.4
26.0
Oligochaeta (small spp.)
5.3
0.2
Planarians
13.6
0.5
Small leeches
67.3
11.4
Chironomid larvae (small spp.)
49.9
6.9
Sand-case caddis
16.5
383.3
3.3
42.6
Hexagenia, etc. (nymphs)
9.0
8.1
Agrionid nymphs
4.4
2.2
Sialis larvae
2.2
1.3
Asellus sp.
2.2
0.2
Hyalella knickerbockeri
212.9
8.5
Total
767.5
79.6
520
Fox Lake (Including Mineola Bay), August — October, 1916. Bottom Fauna
28 Collections, Littoral Zone, 1 to 7 ft. Some Vegetation
Number per square yard
Pounds per acre
Campeloma subsolidum
0.8 0.8
2.3 2.3
Musculium transversum
Musculium jayanum
Sphaerium sp.
Pisidium sp.
Amnicolidae
Valvatidae
Physa spp.
0.8
1.6
0.8
5.5 40.6
25.1
4.6
2.2
0.4
0.8
0.4
0.2 3.6
1.4
0.3
0.1
Oligochaeta (small spp.)
15.6
0.5
Planarians
1.6
0.1
Leeches (small spp.)
14.7
2.5
Leeches (large spp.)
0.8
1.5
Chironomid larvae (small spp.)
9.2
1.3
Palpomyia larvae
0.8
0.1
Sialis larvae
0.8
278.2
0.5
18.0
Caenis larvae
7.7
*
0.6
Caddis larvae, misc.
0.8
0.1
Agrionid nymphs
3.1
1.5
Libellulid nymphs
0.8
0.4
Asellus sp.
0.8
0.1
Hyalella knickerbockeri
221.5
8.8
Total
319.6
23.9
521
2. Weed Fauna
Head of Pistakee Lake, August 17, 1916, in Ceratophyllum
Weed Fauna, Upper 9 Inches (Depth, 3.5 ft.)
No. per sq. yard
Pounds per acre
Amnicola limosa
Physa sp.
1,440
1,920
480
54.7
81.1
26.4
Chironomid larvae (small spp.)
Small beetle
Plea striata
Caddis sp. (basket case)
Hyalella knickerbockeri
720
120
120 58,080
120
57,000
23.7
6.
8.4 2,330.1
12.0
2,280.0
60,000
2,411.2
North Side of Nippersink Lake, August 18, 1916, in Potamogeton and
Ceratophyllum
Weed Fauna, Upper 9 Inches, (Depth, 3.5 ft.)
No. per sq. yard
Pounds per acre
Amnicola limosa
Physa spp.
600
840
240
22.8
36.0
13.2
Chironomid larvae (small spp.)
Hyalella knickerbockeri
2,880
22,080
19,200
95.0
863.0
768.0
Total
22,920
899.
522
BIBLIOGRAPHY
Alvord, John W., and Burdick, Chas. B.
'15. The Illinois River and its bottomlands. Rep. 111. Rivers and
Lakes Commission, p. 1 — 141.
Baker, F. C.
'16. The Relation of mollusks to fish in Oneida Lake. N. Y. State
Coll. Forestry, Syracuse Univ., Tech. Pub. No. 4, p. 15 — 366.
'18. The productivity of invertebrate fish food on the bottom of
Oneida Lake, with special reference to mollusks. N. Y. State
Coll. Forestry, Syracuse Univ., Tech. Pub. No. 9, p. 1 — 264.
Board of Officers of the Corps of Engineers, U. S. Army
'05. Report upon a survey for a navigable waterway from Lock-
port, 111., to the mouth of the Illinois River. House of Repre-
sentatives, Doc. No. 263, 59th Congr., 1st Session, p. 1 — 544,
and charts.
Forbes, Stephen A., and Richardson, R. E.
'13. Studies on the biology of the upper Illinois River. Bui. 111.
State Lab. Nat. Hist., 9 (Art. X) : 481—574.
'19. Some recent changes in Illinois River biology. Bui. 111. Nat.
Hist. Surv., 13 (Art. VI): 139—156.
Legislative Investigating Committee
'11. Report on the submerged and shore lands. Published under
direction of House of Representatives, 47th General Assembly,
State of Illinois. Vol. I, p. 1—191.
Muttkowski, R. A.
'18. The fauna of Lake Mendota. A qualitative and quantitative
survey, with special* reference to the insects. Trans. Wis. Acad.
Sci. Arts and Letters, 19 (Pt. I) : 374—482.
Petersen, C. G. Joh., and Jensen, P. Boysen
'11. Valuation of the sea. I. Animal life of the sea bottom, its
food and quantity. Rep. Danish Biol. Station, 20 (1911) : 1—76.
Petersen, C. G. Joh.
'14. Valuation of the sea. II. The animal communities of the sea
bottom and their importance for marine zoography. Rep. Dan-
ish Biol. Station, 21 (1913) : 1—44.
'18. The sea bottom and its production of fish food. A survey of
the work done in connection with valuation of Danish waters
from 1883 to 1917. Rep. Danish Biol. Station, 25 (1918) : 1—62.
PROFILE OF A SECTION OF THE ILLINOIS RIVER
Profile of the Illinois River from Chillicothe to Lagrange dam, showing
elevations of water surface at low gage of 1901, channel depths, and general
character of upper layer of bottom soils and sediments. The profile marks out
clearly the three deep, flat-sloped, mud-bottomed, natural pools in which the
richest accumulations of small bottom-animals were found both in 1913 and
1915, viz.: the Peoria Lake pool, lying behind the great bar thrown up by Farm
Creek; the Havana pool, behind the great natural wier formed by the wash
from Spoon River; and the Sangamon pool, lying behind the high bar thrown
up by the mouths of the Sangamon. The data here used (elevations, soundings,
and borings) are from the report of the U. S. Engineers' Survey for a deep
waterway, House Document No. 263, 59th Congress, 1st session, Washington,
1905.
5094 096
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